Iam using Class StringClobType which uses Clob type for String by implementing UserType. I used this custom user type in one of my class Item which maps String Array to table of Clob types.
* @hibernate.array table="ITEM_DATA" cascade="all"
* @hibernate.collection-index column="DATA_IDX"
* @hibernate.collection-key column="DATA_ID"
* @hibernate.collection-element column="DATA" type="com.util.StringClobType"
*/

Its working fine in Windows environment but throwing exception in Solaris.
below is the stacktrace of exception.

[b]Hibernate version:[/b]
2.1
[b]Mapping documents:[/b]

[b]Code between sessionFactory.openSession() and session.close():[/b]

[b]Full stack trace of any exception that occurs:[/b]
net.sf.hibernate.JDBCException: could not initialize collection: [com.Item.datums#2396]
at net.sf.hibernate.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:287)
at net.sf.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:3268)
at net.sf.hibernate.impl.SessionImpl.getCollection(SessionImpl.java:3937)
at net.sf.hibernate.type.PersistentCollectionType.resolveIdentifier(PersistentCollectionType.java:170)
at net.sf.hibernate.impl.SessionImpl.initializeEntity(SessionImpl.java:2205)
at net.sf.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:315)
at net.sf.hibernate.loader.Loader.doQuery(Loader.java:305)
at net.sf.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:133)
at net.sf.hibernate.loader.Loader.loadCollection(Loader.java:990)
at net.sf.hibernate.loader.Loader.loadCollection(Loader.java:965)
at net.sf.hibernate.loader.OneToManyLoader.initialize(OneToManyLoader.java:93)
at net.sf.hibernate.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:284)
at net.sf.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:3268)
at net.sf.hibernate.impl.SessionImpl.getCollection(SessionImpl.java:3937)
at net.sf.hibernate.type.PersistentCollectionType.resolveIdentifier(PersistentCollectionType.java:170)
at net.sf.hibernate.impl.SessionImpl.initializeEntity(SessionImpl.java:2205)
at net.sf.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:315)
at net.sf.hibernate.loader.Loader.doQuery(Loader.java:305)
at net.sf.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:133)
at net.sf.hibernate.loader.Loader.loadCollection(Loader.java:990)
at net.sf.hibernate.loader.Loader.loadCollection(Loader.java:965)
at net.sf.hibernate.loader.CollectionLoader.initialize(CollectionLoader.java:83)
at net.sf.hibernate.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:284)
at net.sf.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:3268)
at net.sf.hibernate.impl.SessionImpl.getCollection(SessionImpl.java:3937)
at net.sf.hibernate.type.PersistentCollectionType.resolveIdentifier(PersistentCollectionType.java:170)
at net.sf.hibernate.impl.SessionImpl.initializeEntity(SessionImpl.java:2205)
at net.sf.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:315)
at net.sf.hibernate.loader.Loader.doQuery(Loader.java:305)
at net.sf.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:133)
at net.sf.hibernate.loader.Loader.loadEntity(Loader.java:911)
at net.sf.hibernate.loader.Loader.loadEntity(Loader.java:931)
at net.sf.hibernate.loader.EntityLoader.load(EntityLoader.java:59)
at net.sf.hibernate.loader.EntityLoader.load(EntityLoader.java:51)
at net.sf.hibernate.persister.EntityPersister.load(EntityPersister.java:419)
at net.sf.hibernate.impl.SessionImpl.doLoad(SessionImpl.java:2117)
at net.sf.hibernate.impl.SessionImpl.doLoadByClass(SessionImpl.java:1991)
at net.sf.hibernate.impl.SessionImpl.internalLoad(SessionImpl.java:1953)
at net.sf.hibernate.type.ManyToOneType.resolveIdentifier(ManyToOneType.java:69)
at net.sf.hibernate.type.EntityType.resolveIdentifier(EntityType.java:204)
at net.sf.hibernate.impl.SessionImpl.initializeEntity(SessionImpl.java:2205)
at net.sf.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:315)
at net.sf.hibernate.loader.Loader.doQuery(Loader.java:305)
at net.sf.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:133)
at net.sf.hibernate.loader.Loader.doList(Loader.java:1033)
at net.sf.hibernate.loader.Loader.list(Loader.java:1024)
at net.sf.hibernate.hql.QueryTranslator.list(QueryTranslator.java:854)
at net.sf.hibernate.impl.SessionImpl.find(SessionImpl.java:1544)
at net.sf.hibernate.impl.SessionImpl.find(SessionImpl.java:1521)
at net.sf.hibernate.impl.SessionImpl.find(SessionImpl.java:1517)
at com.HibernateDPO.findById(HibernateDPO.java:48)
at com.Fulfillment.findByID(Fulfillment.java:74)
at com.EventAdapter.getWorkflow(EventAdapter.java:274)
at com.Adapter.sessionCompleted(Adapter.java:164)
at com.Handler.sessionCompleted(Handler.java:191)
at com.Rules.sessionCompletedCallBack(Rules.java:130)
at com.Rules.sessionCompletedCallBack(SyncSessionRules.java:84)
at com.sessionCompletedCallBack(Session.java:447)
at com.Server.sessionCompletedCallBack(Server.java:390)
at com.$5.run(GatewayService.java:140)
at com.PersistenceBrokerFacade.executeInTransaction(PersistenceBrokerFacade.java:114)
at com.GatewayService.sendSessionCompletedCallBack(GatewayService.java:133)
at com.Gateway.doPost(Gateway.java:392)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:760)
at com.gateway.Gateway.service(Gateway.java:175)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at weblogic.servlet.internal.ServletStubImpl$ServletInvocationAction.run(ServletStubImpl.java:971)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:402)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:305)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:6350)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:317)
at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:118)
at weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:3635)
at weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:2585)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:197)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:170)
Caused by: java.sql.SQLException: Invalid column type
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:134)
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:179)
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:269)
at oracle.jdbc.driver.OracleStatement.getCLOBValue(OracleStatement.java:4304)
at oracle.jdbc.driver.OracleResultSetImpl.getCLOB(OracleResultSetImpl.java:1025)
at oracle.jdbc.driver.OracleResultSetImpl.getClob(OracleResultSetImpl.java:1190)
at oracle.jdbc.driver.OracleResultSet.getClob(OracleResultSet.java:1962)
at weblogic.jdbc.wrapper.ResultSet_oracle_jdbc_driver_OracleResultSetImpl.getClob(Unknown Source)
at com.util.StringClobType.nullSafeGet(StringClobType.java:52)
at net.sf.hibernate.type.CustomType.nullSafeGet(CustomType.java:92)
at net.sf.hibernate.collection.AbstractCollectionPersister.readElement(AbstractCollectionPersister.java:363)
at net.sf.hibernate.collection.ArrayHolder.readFrom(ArrayHolder.java:124)
at net.sf.hibernate.loader.Loader.readCollectionElement(Loader.java:380)
at net.sf.hibernate.loader.Loader.getRowFromResultSet(Loader.java:235)
at net.sf.hibernate.loader.Loader.doQuery(Loader.java:281)
at net.sf.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:133)
at net.sf.hibernate.loader.Loader.loadCollection(Loader.java:990)
at net.sf.hibernate.loader.Loader.loadCollection(Loader.java:965)
at net.sf.hibernate.loader.CollectionLoader.initialize(CollectionLoader.java:83)
at net.sf.hibernate.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:284)

[b]Name and version of the database you are using:[/b]
oracle9i
[b]The generated SQL (show_sql=true):[/b]

[b]Debug level Hibernate log excerpt:[/b]

Looks like your JDBC driver doesn't think that the value returned was actually a CLOB.