I had a similar problem where I would try to open a file in a MS Office product and it would time out before showing the OS listing. This would take 30-45 seconds and it is a bug in the way MS Office accesses the file system.
The fix was to remove any network drives that were no longer available. If you had three network shares on your system and one of them was removed at the host end, but not at the client end then the client will be slow in accessing the file system.
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