CE 5 Speed slow CE 4 was fast

All

I have various clients that have MS CE installed and configured to work with a custom workspace.  With CE 1, 2, 3, 4.  As each build was released the speed got faster, most noticeable in CE4.  However, I have just upgraded to CE5 and OMG its worse than ever, takes c. 5-10 minutes to open a file.

This was even with a clean install

WHY?

Ian