Graphics glitch when resizing with Windows Control

Well I have code set up in my game so when you press 2 the game goes from 640 x 480 to 1280 x 960, and then when you press 1 it goes back to 640 x 480. That works just fine, however I noticed that some pixels seem to be missing from objects when they go back down to 640 x 480 after having been enlarged. Is there a way around that?

For the time being I just switched to HWA and have the window maximize. When you restore after it's maximized, no problems. For some reason though, with the Windows Control and resizing, it causes issues.