"/System/Library/Extensions/PACESupport.kext"

After finally installing Snow Leopard today and updating to 10.6.4, I've been getting this error message appear sporadically:

System extension cannot be used.
The system extension "/System/Library/Extensions/PACESupport.kext" was installed improperly and cannot be used. Please try re-installing it, or contact the product's vendor for an update.

How can I fix this?

Thanks.