xactisolevel --- ehh?

Hello,

I've just switched from 7.2 to 7.3 and I get this exception:

java.sql.SQLException: ERROR:  Option 'xactisolevel' is not recognized

  at org.postgresql.core.QueryExecutor.execute(QueryExecutor.java:94)
  at org.postgresql.Connection.ExecSQL(Connection.java:398)
  at org.postgresql.Connection.ExecSQL(Connection.java:381)
  at org.postgresql.Connection.getTransactionIsolation(Connection.java:921)
  at pl.e11.dbo.Storable.create(Storable.java:1119)
  ...

As you can see in stack trace, the exception is being thrown while getting
transaction isolation level; the line 1119 is:

 int ti = cn.getTransactionIsolation();

Of course it worked earlier, troubleless. I don't know if this is 7.3
related problem (by 7.3 i mean both psql and jdbc drivers); i don't actually
know what xactisolevel is --- does anyone has any suggestion about how to
solve this? Thank you very much in advance 8)

Tomek.