With the ACE utility not wanting to run, in Vista just because you disable the ever annoying UAC, you still need to run the program in administrator mode. I belive it requires elevated permissions, and thats what I do. I do not have UAC disabled on my machine.

Sorry if this is a stupid question or you have answered it before, is your IRS alligned at the airport? I have a 737 that is very touchy about that. You even have to give the IRS a starting position in the FMC before it will sucessfully align.

Also check your FSX settings and see if something looks amiss in your default units/ Measurements category.