When I boot up and initially log on to a user then switch to another (doesn't matter which order), the computer works okay. When I go back to original user, screen resolution jumps from 1024 x 768 to 640 x 480 pixels and I can't reset back to its original setting. When I try to go back to 1024 x 768 and hit apply, it stays at 640 x 480. Only rebooting will get it back.

Does anyone know what I can do to fix this? This has been happening for quite a while now and is really bugging me, because I basically can't switch users!

Download and re-install your manufactures Video drivers
It would also be wise to remove any current video drivers first.

Please put your System Specs in your Profile

For any further support on this.