I am not great with Windows 7, but normally graphic issues is a drivers issue. You may want to try reloading the Video drivers. Now I have seen Windows 7 do some strange s@#$# here at the house with our 3 Windows 7 systems. Major Updates..like 1000+ and such.
Take it from a LONG TIME Windows Tech/User: Never bye a new Microsoft OS within 1 year of it's release! too many F@#$% bugs! I saw it first hand with 3.1 & 3.11 Workgroups to 95, 95 to 98, 98 to Millennium, Millennium to 2000, 2000 to XP. Yea that long! Personally I am still ON XP just for that reason!