An I/O error occured while sending to the backend

Hello,

I have a problem that I am not able to solve. I have this exception:

org.postgresql.util.PSQLException: An I/O error occured while sending to
the backend.
    at
org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:216)
    at
org.postgresql.jdbc2.AbstractJdbc2Connection.executeTransactionCommand(AbstractJdbc2Connection.java:649)
    at
org.postgresql.jdbc2.AbstractJdbc2Connection.rollback(AbstractJdbc2Connection.java:686)
    at com.evermind._id.rollback(.:196)
    at com.evermind._ja.rollback(.:104)
    at com.evermind._bs._gbc(.:118)
    at com.evermind.server.ApplicationServerTransaction._gcc(.:334)
    at com.evermind.server.ApplicationServerTransaction._gbc(.:296)
    at com.evermind.server.ApplicationServerTransaction.rollback(.:279)
    at
com.evermind.server.ApplicationServerTransactionManager.rollback(.:285)
    at
cz.iiprg.util.importer.ejb.ImporterEJB.rollbackTransaction(ImporterEJB.java:173)
    at
Importer_StatefulSessionBeanWrapper34.rollbackTransaction(Importer_StatefulSessionBeanWrapper34.java:416)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:324)
    at com.evermind._bt._uab(.:79)
    at com.evermind._bf.run(.:62)
Caused by: java.io.IOException: Stream closed
    at sun.nio.cs.StreamEncoder.ensureOpen(StreamEncoder.java:38)
    at sun.nio.cs.StreamEncoder.flush(StreamEncoder.java:151)
    at java.io.OutputStreamWriter.flush(OutputStreamWriter.java:213)
    at org.postgresql.core.PGStream.flush(PGStream.java:501)
    at
org.postgresql.core.v3.QueryExecutorImpl.sendSync(QueryExecutorImpl.java:674)
    at
org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:189)
    ... 17 more

It is strange that it occurs randomly and only when the server is loaded.

Radek