Socket read fails

Hi there, wondering if anyone could shed some light on selects intermittently not returning any data on our production server.

Symptoms are:   

- occurs in several different parts of our codebase but apparently its the same jdbc codepath [below]
- these codepaths execute fine the vast majority of the time
- thread blocks on read forever
- database doesnt show any query running.
- system has a couple of high load processes that run every day and we only see the errors there, though the majority of the systems' queries are done then.

Any suggestions for what I could do to fix or help diagnose the problem greatly appreciated. We saw these problems with v7, v8 and now seeming more frequently (ie every few days) with 8.1 jdbc and 8.1 server.

We run ES Linux 3.

cheers
Colin.

"Thread-571" prio=1 tid=0x085745b0 nid=0x124e runnable [759fe000..759ff87c]
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.read (SocketInputStream.java:129)
        at java.io.BufferedInputStream.fill(BufferedInputStream.java:183)
        at java.io.BufferedInputStream.read1(BufferedInputStream.java:222)
        at java.io.BufferedInputStream.read (BufferedInputStream.java:277)
        - locked <0x847ac890> (a java.io.BufferedInputStream)
        at org.postgresql.core.PGStream.Receive(PGStream.java:445)
        at org.postgresql.core.PGStream.Receive (PGStream.java:427)
        at org.postgresql.core.PGStream.ReceiveTupleV3(PGStream.java:369)
        at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1283)
        at org.postgresql.core.v3.QueryExecutorImpl.fetch (QueryExecutorImpl.java:1447)
        - locked <0x847aa0b0> (a org.postgresql.core.v3.QueryExecutorImpl)
        at org.postgresql.jdbc2.AbstractJdbc2ResultSet.next(AbstractJdbc2ResultSet.java:1840)
        at org.ofbiz.entity.util.EntityListIterator.next(EntityListIterator.java:269)