Pro Tools (Not Responding)

[XFM Production]

My Pro Tools (8.1.1) keeps getting the spinning wheel. This can last from anywhere from 5 seconds to over an hour and occurs every 1-10 minutes. Then all of a sudden it will start working again and return to normal.

When I alt-apple-escape, it simply shows that Pro Tools is not responding. In the activity monitor, all systems appear normal.

I work for a large radio company with many different brands in different studios and I am the only one with this problem.

Our IT department are simply stumped. I have had my Mac replaced, re-imaged, formatted etc etc yet the problems keeps occurring.

There is no pattern to how this happens. I can be either dragging audio from an external firewire drive, accessing one the many network servers in the building, or simply pressing play.

I have done all the system optimisation steps like disable blu tooth, disable spotlight etc.

Nothing helps.

There are many many Pro Tools users in the building and an entire broadcast / engineering / IT department and no one can work out what the problem is and how to fix it.

Can anyone help???