User profiles Problem

Hi

When I set user profiles up in Control panel through the password icon and rsstart the PC the monitor settings change. The monitor lights just flash, the monitor dosn’t seem to cope with the settings and gives me a black screen. If I then start up in safe mode and take the user profiles off and restart, the monitor works OK. Does seting profiles adjust the monitos frequency, this seems very weird to me. I thought the profiles would take the defaults settings from windows. The monitor and graphics card can cope with up to 1024*768 setting without any problems, but I usualy run the machines at 800*600.