Thanks Michael,
I normally experience this when I'm 'copying and paste' files on Window
explorer.
Restarting the PC seems to solve the problem, but it's temporal solution.
Some people report this behaviour when they got infected with the
Blaster virus. Is the Remote Procedure Call (RPC) service running? How's
your anti-virus software? Any unusual entries in the Event Logs?
Other possibles:
Do the machines have enough RAM? What does the Performance tab of the
Task Manager (taskmgr.exe) tell you?
Any chance of misbehaving programs (e.g. SpyWare) running on these
machines? Can you identify the entries in Task Manager's Processes tab?
Any obvious memory hogs on that page?