Hi there,
I'm not sure if this will fix your problem, but if you're using AD and have not already done so, implement Folder Redirection for My Documents, Desktop, and Application Data and then remove those folders from the Roaming Profile (all done via GP) - you should see some considerable improvement in file access times, ast least for network files (probably local files as well, given the level of integration that Windows systems have).
Hope this helps...