Unexpected EOF on client connection

I am getting many entries in my log of this type:

2009-12-01 00:13:19 GMTLOG: unexpected EOF on client connection
2009-12-01 00:13:19 GMTLOG could not receive data from client: No
connection could be made because the target machine actively refused it.

I tend to get these message in batches of 2 to 8 - checking the number
of connections at the time, they do not appear to be overloaded.

I am running 8.4.1 on Windows 2K3 with a C# application using Npgsql.
All connections are to the localhost and there is no firewall.

Help!

Howard Cole
www.selestial.com