I am having problem using hibernate varbinary to serializable column mapping.
It is able to store and retrieve the data fine in one session.
But if I try to retrieve the existing data from the database table, then it gives org.hibernate.type.SerializationException:

Any suggesstions/comments?

Following are the details:

Hibernate version:
3.0.5

Mapping documents:
<hibernate-mapping>
<class name="model.VaRModel" table="VaRModel" dynamic-update="true" dynamic-insert="true" select-before-update="false">
<id name="Id" column="Id" type="java.lang.Long" unsaved-value="null"><generator class="identity"></generator></id>
<property name="distribution" column="distribution" type="serializable" />
</class>
</hibernate-mapping>

Full stack trace of any exception that occurs:
org.hibernate.type.SerializationException: could not deserialize
at org.hibernate.util.SerializationHelper.deserialize(SerializationHelper.java:211)
at org.hibernate.util.SerializationHelper.deserialize(SerializationHelper.java:234)
at org.hibernate.type.SerializableType.fromBytes(SerializableType.java:78)
at org.hibernate.type.SerializableType.get(SerializableType.java:39)
at org.hibernate.type.NullableType.nullSafeGet(NullableType.java:77)
at org.hibernate.type.NullableType.nullSafeGet(NullableType.java:68)
at org.hibernate.type.AbstractType.hydrate(AbstractType.java:80)
at org.hibernate.persister.entity.BasicEntityPersister.hydrate(BasicEntityPersister.java:1690)
at org.hibernate.loader.Loader.loadFromResultSet(Loader.java:991)
at org.hibernate.loader.Loader.instanceNotYetLoaded(Loader.java:942)
at org.hibernate.loader.Loader.getRow(Loader.java:855)
at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:305)
at org.hibernate.loader.Loader.doQuery(Loader.java:412)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:218)
at org.hibernate.loader.Loader.doList(Loader.java:1593)
at org.hibernate.loader.Loader.list(Loader.java:1577)
at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:395)
at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:271)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:844)
at org.hibernate.impl.QueryImpl.list(QueryImpl.java:74)
at service.HibernateService.main(HibernateService.java:50)
Caused by: java.io.EOFException
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(Unknown Source)
at java.io.ObjectInputStream.readClassDesc(Unknown Source)
at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)
at java.io.ObjectInputStream.readObject0(Unknown Source)
at java.io.ObjectInputStream.readArray(Unknown Source)
at java.io.ObjectInputStream.readObject0(Unknown Source)
at java.io.ObjectInputStream.defaultReadFields(Unknown Source)
at java.io.ObjectInputStream.readSerialData(Unknown Source)
at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)
at java.io.ObjectInputStream.readObject0(Unknown Source)
at java.io.ObjectInputStream.readObject(Unknown Source)
at org.hibernate.util.SerializationHelper.deserialize(SerializationHelper.java:204)
... 20 more

Name and version of the database you are using:
Sybase : Adaptive Server Enterprise/12.5.3

Are you sure that the data already in that field is actually serialized? If it's just random binary data, you can't just deserialize it and have it work. The exception certainly suggests that the existing data is not a serialized java object.