Hello Red,
After more than 30 Years IT experiences... i can tell you that this is a problem that now and then appears.
I've learned that the best thing to avert such problems as you now mention is to install the programs always to the C drive and Data or documents to your D drive.
As you know as a It person, it's always possible to have some kind of protocol conflict... windows says "if not then " ... and the installed software wants a "don't "
I think the greatest nightmare of software developpers is always a new Windows version :-)
grtz
eric