Hi Stefan
Well I can't believe the difference - like night and day.
I reset options as you suggested.
I closed Topstyle
I added the program files\topstyle folder to the exclusion list in Microsoft Security Essentials.
I restarted - and it's FAST.
I've opened a few files - both recent CSS and HTML files.
As I've just reset, the preview is showing and using the IE rendering engine - and it's still fast.
I'll post back in here if things go slow again.
Anyone else care to try if they're suffering the freezing/super slow speed?
Question now is - how do we get this to be reproducible for you to fix for everyone else!

Marky_UK