If you run MS Office on your Mac (because, when you are working on someone else's non-Mac computer--they are hard for some of us to avoid--you don't want to fumble around in Word and Excel), you need to run the "Microsoft Office 2008 12.2.3 update."
Note, software update via Mac will not do it. Open Word and go to Help, seek out "update" there and go to it. This update seems to have come out on November 10. (Nobody tells me nothing. My auto update is only once a month...)
Afterwards, you'll miss enjoy of "the fun color wheel of wait" when using Excel. Entourage opens much, much faster. Word, too.
Note, on Entourage you may have to reenter your POP passwords in your keychain.
Here's the official word:
Also, there is an Open XML Converter Update.
MacRumor's forum is always interesting and sometimes useful with these updates: