The other thing I just thought of regarding this issue... would be font related...
If you've installed new fonts in your user's font folder (/users/yourname/library/fonts) I would suggest removing them and seeing if that helps.
That is one of the things the program is doing at startup. So if there's an incompatible font that Word / Excel / etc can't load, it might take a few seconds for it to time out before moving on to the next font to load.
This has actually happened to me. I had to remove all my fonts, and systematically reload one at a time to see which font was causing the problem.
This would also explain why creating a new user has solved the problem and deleting the prefs has not.