menu Bar and dock problems - MenuBar won't highlight and Dock freezes

Just started having this problem - but had it with Leopard and not sure what I did to fix it. Suddenly the Magnified Dock is freezing - won't slide along with the mouse pointer. Also the menu bar won't highlight the choices of a drop-down menu...

I've tried restarting many times - no change. I believe I have to trash a preference file - but not sure which one! This is almost like when I had the Logitech software installed - but that's gone and trashed - so that cannot be the cause.

Sometimes the curser remains a separation line instead of moving to a pointer or the hand - there are several things related here I believe.

Thanks for any help - or if you need more info, let me know. This is really annoying and I'd like to restore this soon!

Steve