Microsoft has done a lot of work with Vista SP1, so much so that a lot of security programs don't work properly with SP1 although they used to work with Vista RTM. Kernel changes and some networking tweaks are basically the reasons why these programs aren't working. The list may not be completely exhaustive, but Microsoft's Support Center lists these programs.
Programs that are blocked from starting after you install Windows Vista SP1
- BitDefender AV or Internet Security 10
- Fujitsu Shock Sensor 126.96.36.199
- Jiangmin KV Antivirus 2008 or v10
- Zone Alarm Security Suite 7.1.078
Programs that do not run after you install Windows Vista SP1
- Iron Speed Designer 5.0.1
- Xheo Licensing 3.1
- Free Allegiance 2.1
Programs that have a loss of functionality after you install Windows Vista SP1
- NYT Reader v1
- Rising Personal Firewall 2007
- Novell ZCM Agent 10.01
There may be other programs that Microsoft has not identified and still have problems with Vista SP1. A few programs may also not display the incompatibility dialogs, but may contain potential issues with Vista SP1. If you are using any of the above products and have problems then, Microsoft's list with explanation and solutions can be found here.