Slow Network performance

We have several Windows 98 machines in our office on a workgroup network with a Win2K server. The machines have Pentium III processors, with 256 meg memory. One of these machines is sooooo much slower than the others when running our office application, it can take up to 4 or 5 times longer for it to get an account and display it. They all have 3-com 10/100 mbs network cards and according to the lights on the switch, they're all running 100 mbs.

It's got the latest Norton Corp. Edition antivirus, and is virus free. I've ran spy bot to clean up any of those issues.

Any suggestions as to what would cause this machine to be so much slowing?

Thanks