Windows Explorer not responding and slow

We have 16 recently new(Within 6 months) Dell computers and have developed an issue on at least 2 of them..

The Computers are running Windows 7 Professional on a company domain..
All have Intel i5 processors and at least 4 Gb of memory..
Also running Office 2003

The problem that has come up on at least 2 of the computers is an extremely slow access when trying to add a file attachment to an email or just open a file in excel or word..

When you try attaching a file to an email it takes at least a minute for the explorer window to allow you to select the file..
If I let it do it's thing it finally comes around and allows the selection of a file.. If I try canceling it we get an error that windows explorer needs to close and it closes and refreshes the screen.

It does not appear to be an outlook/office issue because it does the same thing in word or excel when trying to open a file or just in windows explorer itself..

Tried repairing the office installation and scanned for any changed system files using sfc /scannow.. No problems found and problem still exists

I scanned for malware and disabled unnecessary startup items with no effect..

Did a Chkdsk scan and that didn't help..

Not sure when this started happening so I can't do a system restore.. Not sure if an update is causing this..

I was going to try and reformat and reinstall everything, but found another computer with the same issue..

Any help would be appreciated..

Thanks