Yes, some programs will break after you install SP1, but it could be worse.
Microsoft's just-announced news that certain programs will break after you install SP1 is a pain, but we're not panicking yet.
The news, posted on the Microsoft Support site, warns of a "loss of functionality" for certain programs under SP1, including some that are blocked from running, and others that simply just don't work.
It's not a huge list, though there are a few popular anti-virus programs that will be blocked from running after installation of SP1, including ZoneAlarm Security Suite 7.1, Trend Micro Internet Security 2008, and BitDefender AV/ Internet Security 10.
Software companies are making fixes available, but the info wasn't particularly clear when we checked. The Microsoft site specifies that ZoneAlarm version 7.1.218.0 or later will solve the SP1 issue, but the Vista support page on the ZoneAlarm site didn't mention anything about this or SP1 when we checked. The BitDefender page is more helpful, with details on the free upgrade from V10 to 2008.
The SP1 upgrade-dance also got trickier this week after reports that a pre-SP1 update was causing problems on some PCs. Microsoft has admitted the "error" and stopped the automatic update while it looks into the problem.
Some PCs will be also locked out of automatically downloading the Vista SP1 update when automatic SP1 downloads via the Windows Update service begin in April. The issue is due to "badly installed" third party drivers on some PCs.
If Windows Update detects that a PC has one of these drivers, it won’t offer SP1 for download (though it will still be available through Microsoft’s download center). Once the problematic drivers are updated and installed by Windows Update, those PCs will be “unblocked” and allowed to download SP1.
If all this has you pining for XP, we've got good news. This week Microsoft made Service Pack 3 Release Candidate 2 for Windows XP available for public download.