Unknown winsock error 10061

Hi

reading google.. i come to here... maybe i can help more about this issue.

on server pglog:

2009-07-15 09:40:27 BRTLOG: could not receive data from client: Unknown
winsock error 10061
2009-07-15 09:40:27 BRTLOG: unexpected EOF on client connection
2009-07-15 09:41:35 BRTLOG: could not receive data from client: Unknown
winsock error 10061
2009-07-15 09:41:35 BRTLOG: unexpected EOF on client connection
2009-07-15 09:44:05 BRTLOG: could not receive data from client: Unknown
winsock error 10061
2009-07-15 09:44:05 BRTLOG: unexpected EOF on client connection
2009-07-15 09:45:09 BRTLOG: could not receive data from client: Unknown
winsock error 10061
2009-07-15 09:45:09 BRTLOG: unexpected EOF on client connection
2009-07-15 09:45:14 BRTLOG: could not receive data from client: Unknown
winsock error 10061
2009-07-15 09:45:14 BRTLOG: could not receive data from client: Unknown
winsock error 10061
2009-07-15 09:45:14 BRTLOG: unexpected EOF on client connection
2009-07-15 09:45:14 BRTLOG: unexpected EOF on client connection
2009-07-15 09:50:30 BRTLOG: could not receive data from client: Unknown
winsock error 10061
2009-07-15 09:50:30 BRTLOG: unexpected EOF on client connection
2009-07-15 09:51:34 BRTLOG: could not receive data from client: Unknown
winsock error 10061
2009-07-15 09:51:34 BRTLOG: unexpected EOF on client connection
2009-07-15 09:51:34 BRTLOG: could not receive data from client: Unknown
winsock error 10061
2009-07-15 09:51:34 BRTLOG: unexpected EOF on client connection

Enviroment:
The server running W2003 R2 with Intel Quad Core Q6600 @ 2,4Ghz - 4Gb RAM
PostgreSQL 8.4.0
before was used PG 8.3 and happens too.

Notes:
* 40 to 60 simultaneus conection to database
* use libpq.dll to conect to server.
* use Zeos 7 / Delphi 2009 application. this application makes 2
connection to a same database (for transaction isolation)
* error dont happen in server and 20 machines winXP
* error happen only in 5 machines with winXP
* in this 5 machines: Removed Antivirus, Firewall and windows update
activated.
* changed hub port cables to prevent hardware fails.

then i decided format 1 machine, instaled winxp and the problems not
happend! very stange...
i thinking format these other machines... but i want detect what dll of
windows is outdated or with problem...

another strange error in same 5 clients, i think that has relation... let´s
go..
before i received message in client "could not receive data from server
WSAStartup not yet called (0x0000276D10093)" and the server log register
"winsock error 10061".
this message occours only if a client database connection is stand by for
a time (1 minute or more)
to resolve this is added a timer to make the stupid query "select now()"
every 20 seconds, only to simulate activity on connection, and not happend
more...

if necessary i can make any test to try resolve this...
any idea is welcome.

Franklin Haut