In my case it's a little different.
Using my msn live account to sign in with.
I can set UAC to off and the Apps still work but if I turn it back on again most of the Apps will not open again for anything, quick flash then then back to start screen again.
This problem is wide spread for people using the CP and is definitely caused by UAC but for some people turning it off seems to cause the problem, with me turning UAC off causes no problems with the Apps but turning it on again causes the problem. No amount of messing with UAC after that point made any difference at all.
Luckily I made a system image to restore to before messing with UAC and problem solved. For me it's turn UAC off and don't mess with it again. I like the weather App "which stopped working now fixed" and the pinball " still worked" is pretty fun. I can't stand when stuff doesn't work so I had to get to the bottom of it.
These types of bugs are fairly typical in the earlier builds. Windows 7 in the earlier builds had a similar problem where if you turned off UAC then the Gadgets would not open.