Well, actually, it goes up to 28%, then back down to 27%. Running Windows 7, the problem ended up being that I didn't have write access to the start menu... strange since I was running that install as Administrator.
Verify in the system application event logs.
To fix it I used this awesome little app called, rightfully enough, "Take Ownership"...
http://www.howtogeek.com/howto/windows-vista/add-take-ownership-to-explorer-right-click-menu-in-vista/
