Hmm. Interesting - today, WUMT was disabled (couldn't even start and gave no error message) on one of the laptops I use. I took a guess and got it to work again by the simple expedient of setting the properties in the associated .EXE files to Administrator. ...
I presume WUMT will probably be similarly disabled on the other laptops I use...
I wonder. This seems redolent of how, a few years back, Microsoft went through a phase of making ad hoc and unannounced changes to MS Messenger protocols, apparently with the sole purpose of frustrating Trillian users from being able to use MS Messenger via Trillian. The Trillian developers just kept patiently providing workarounds to each of the blocks as they were implemented. Eventually MS stopped the mucking about. It was moronic.
MS wasn't the only messenger service provider doing that, either - trying to block Trillian usage, I mean - though they were probably (seemed to be) the worst offenders.