invalid message format and I/O error while comunicating with backend

Hello

I have a small server written in java. It receives data through UDP ports, and queues data until several working threads process the data.
The process involves launching several prepared statements selects/inserts over different db schemas for every data packet received.

The server and the database are both on the same machine. I would like to have a moderate to high level of throughput, as I'm interested in being able to
receive several data per second.

Everything is working ok and fast, but at some moment (sometimes sooner, sometimes later) the server starts to fail with the following messages

org.postgresql.util.PSQLException: invalid message format (for the first failure)
org.postgresql.util.PSQLException: A I/O error has happened while sending to backend (at every following jdbc call)

(Message errors are freely translated from the original spanish messages)

At first I though it was because of connection pooling, but I have tried it with and without pooling with no success.
Every working thread has one connection which last for as long as the program is running. This single connection per thread is used to access several schemas of the same data base.

It seems that sending data to the server faster makes the error to appear sooner.

I have'nt foound any suitable clue about it while googleing.. so I hope someone can help me here

More data:
Java(TM) SE Runtime Environment (build 1.6.0_03-b05)
PostgreSQL 8.1.10 (Ubuntu)
postgresql-8.2-507.jdbc4.jar

commons-dbcp-1.2.2
commons-pool-1.3

Thanks in advance

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