mssql 5 end user workstaion drops connection intermittent

I have a an inventory database that has a sql05 backend and 2 of the main users keep loosing connection. I think it may be a network congestion problem. or a tcp problem. so far nothing has worked that i can think of. it started about 10 days ago. any suggestions would be great. Currently I have been running wireshark on both the server and the workstation, and the conversations appear to be ok.