Microsoft has published a list of software that has problems with Windows Vista SP1. AntiVirus and security software makes up a big portion of the list. Most of the apps already have a solution of simply (hopefully simple that is) updating to the the latest version.
While it doesn’t help Vista’s reputation to have more incompatibilities the list is currently rather small and seems to contain software that puts it’s hooks into the OS. I have to say, makes running Windows in a VM even more attractive, just create a snapshot before the upgrade or save off a copy of the VM itself.