iMac screen turns green on desktop
I just started my iMac after coming home from work and everything went fine until the desktop comes up. Then I have this green (almost fluorescent) cast over my entire screen. During startup and the login screen everything looks normal. Even shutting it down it returns to normal.
Under the display preferences, if I select a profile it will flicker normal and then return to the green.
I had a bad memory chip a couple months ago and that was replaced under warranty, but that is it for problems over the last year.
What steps should I take to trouble shoot this before dragging this monster into the Apple store?
Thanks for any help.
Boy it is tough to type while looking at this screen.
iMac (27-inch Mid 2011), Mac OS X (10.7.4)