Microsoft's most recent update for Windows caused many people using Check Point's ZoneAlarm firewall to lose their Internet connection. The patch fixes a potential DNS-related security breach that affects servers and clients alike, so I'm sure Microsoft was compelled to release it as quickly as possible.
That's little consolation for the many ZoneAlarm users who struggled to regain their network connection. Read more about the problem, and find a link to Check Point's solution, at Robert Vamosi's Defense in Depth blog.
The fact is, even with potentially serious security holes such as this appears to be, you can usually wait a day or two before installing the update to make sure the fix doesn't cause some problems of its own. Simply set Windows Update to download updates automatically but prompt you before installing them, or to alert you when an update is available for download so you can decide when to fetch it and implement it.
In Windows XP, click Start > Run, type sysdm.cpl, and press Enter. Click the Automatic Updates tab and choose either "Download updates for me, but let me choose when to install them," or "Notify me but don't automatically download or install them." You can also choose "Turn off automatic updates," but I recommend either of the semi-automatic methods. When you're done, click OK.
To change your Windows Update settings in Vista, press the Windows key, type windows update, and press Enter. Click Change settings in the left pane, and choose either "Download updates but let me choose whether to install them" or "Check for updates but let me choose whether to download or install them." As with XP, I caution against selecting "Never check for updates (Not recommended)." This is one of the few points on which Microsoft and I agree.
Now get into the habit of watching the tech news wires each Wednesday after Microsoft's Patch Tuesdays to determine whether an update is going smoothly before applying it manually. Sometimes being first isn't such a good idea.