Networks

And what messages are displayed when this occurs? Network timeout? If a timeout, what timed out?

- 4 megs ram

This is a 64-bit machine and OS?

- Windows Server 2003 r2

This is the OS on the Thinkcenter? What else is the server doing?

Does ipconfig /all have the expected output?

How is this machine connected to the LAN and the internet?

Tools:
http://www.broadbandreports.com/tools
http://www.wireshark.org/

Please check the DNS address

Have you checked the Network for Traffic?

If this particular computer is sending/receiving a lot of traffic over the Network this will explain why it's slow to access the Internet sometimes and not others.

The other thing to ask here is does this happen at specific Times over the day or is it just random?

Col

Try out Ccleaner and see if it cures your problem here:
http://www.filehippo.com/download_ccleaner/download/92a389aaa28d085aa9a190ee734a0161/