when i was running vista i had the same problem... thres a difference from being an administrator and "run as administrator"... check the options for that. You might also need to check the compatability mode...
it might help to turn off the thumbnail toolbar thing if you have that enabled, its a cool feature but can cause issues sometimes.
In all honesty i cant remember what i did to make quest work for me when i had vista, but i found a way. Hope these sugestions work for you.
In addition to running as an administrator (and being one) and comparability mode, ensure that Vista's font and font size are set to Micosoft Sans Serif and size 8 (this can cause compatibility issues on some programs) and that your DPI is set to 96 (bigger or smaller will cause things to look a bit funky or not appear correctly at all).
Could also try downgrading from vista's version (3.0, I believe) of the .net framework to XP's default version (2.0, I believe)
Since nobody gave any information but Vista and Quest Disappears! I can't give a great answer...
