Ultra widescreen... (Wrong screen size)

I was playing with a second monitor on my AMD laptop (with ATI drivers). For some reason, after activating the dual head mode from the ATI Catalyst Control Center, the screen in KDE4 (with kwin compositing effects) was garbled and unusable. KDE3 works fine, but, even without the second monitor (and with the dual head mode disabled), the screen acts twice as big (physically, not in resolution). The virtual desktop pager shows my screen as twice it’s actual width, and I can lose my pointer for a moment if I move too far over. The screen resolution is still the same, it just acts like I still have a second monitor. I looked at my xorg.conf, and everything seems okay as far as I can tell. This is really annoying, and I really appreciate a little help.