The Microsoft Office 2007 SP2 update was only released yesterday and is a major upgrade for that package. Most users, individual and corporate, tend to apply Office service packs right away as they aren’t released very often and are usually rock solid.
JKontherun reports already seeing in their comments that a number of corporate users are experiencing a major bug in SP2 that affects the ability to access the Global Address Book effectively rendering corporate email useless. One corporate user says the problem went away when Office 2007 SP2 was removed. I suspect we’ll see a rapid fix for this from Microsoft, I’m surprised a bug this big got through to release.