Users randomly being disconnected from Win2k3 server.

I am working in a 40 workstation environment using dell powerconnect switches, running a domain controller and have all users my documents and desktop redirected to the server. all users have offline files enabled. i have been noticing recently that some users are randomly being kicked into offline mode, at which point they need to manually re-synchronize with the server to be able to access any server based resource. what im trying to figure out is what is causing these users (myself included) to sometimes lose the connection to the server.

currently, the domain controller/file server is connected to a seperate powerconnect switch located on the same rack, and then that switch is patched into the main switch that all the users are connected to. i am wondering if i were to move the server onto the main switch if that would have any affect. does anyone have any ideas as to some other possible causes?