AddToPath doesn't always update

[jweinraub]

I have customers who complain of certain errors during the post installation experience. The reason is the $INSTDIR did not get added to the path at the time of installation.

I can have them manually add it by the control panel but the installation won't. Usually they will need to reboot, reinstall, then the process works.

Any ideas to why, because I can't think of any that make sense. This happens to 1-4% of our users and all of them are solved the same way, but I can not think of a cause to WHY the path didn't add itself during the installation process.