Ok, I tried reinstalling Office (which is 2008, not 2004 btw) to see if that would fix the problem. I tried once using the Remove Office tool, which never worked in the past, but did this time, although it took FOREVER to run. This didn't have any effect on the Quick Look problem. Then an apple store employee here suggested that the Remove Office tool actually leaves quite a few files on your system (true) which in their expereince often are the source of problems, so always delete Office and it's user files in various places manually. I did this, and achived a fairly clean reinstall (had to re-enter my product key, id info, etc.), but this still had no effect on Quick Look.
So I'm pretty sure at this point that it must be an OS X problem. Fixing this is not worth doing an OS X reinstall and system recovery from time machine right now... so other suggestions would be welcome, otherwise, I guess I give up for now.