Shared Drives drop and will not restore

Shared Drives drop and will not restore
I asked this question before, but got absolutely NO attempts to answer it, so I am trying one last time:

On a straight Windows 2000 network with shared drives on the server: with the server timeout set to30 minutes, some units’ shared drives drop out (red X) and when you click, they return ok, others lock up and give an error message similar to the following: “Microsoft Windows Network: The local device name is already in use. The connection has notbeen restored.” On units that are running critical apps locally but with their data files on shared drives, this causes us lost data and sometimes locked apps. I have changed NICS, double-checked NIC settings, played with timeout values, even turnedthe timeout OFF totally, with little to no luck. Any ideas?