Word 2007 unstable on Vista but not XP

I purchased a new Sony Vaio laptop last April. I am on the verge of getting
out the recovery dvds I created when I first bought it and starting over
again.
It came with a trial version of Office 2007 which I tried. It operated just
fine so I purchased the small business version and installed that. It wasn't
long after that I noticed when opening a word doc or starting a new one that
the rotating busy icon keeps running while word is open. I can still type,
edit, backspace and use word like normal except this causes a good amount of
lag time on everything. This problem also causes the taskbar (which I auto
hide) to flash at the bottom which continues even after word is closed until
re-starting the computer. All the other Office products in the suite
work fine.

I had heard about Vista causing problems with programs so I loaded Office
2007 on my desktop running XP and I have no problems. All updates to Vista
and Office have been installed. I was hoping one of the updates would fix
the problem. Office was uninstalled and re-installed on
the Vista system with the exact same problem still showing up. I have tried
to Google this problem and not any luck finding a solution. I saw Word 2007
running fine on my style laptop at Best Buy the other day.

Has anyone else had this problem?

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Thanks
John