Turning a month on iCal makes my graphics crash

Lately on iCal when I turn a page (e.g., to go to the next month) my graphics display flickers with random graphics (especially in the ical window) and at times it freezes the whole display meaning I have to reboot.

It only happens with iCal. It sometimes happens on an iCal alarm as well.

Any ideas? I am on 10.7.5 with all the latest updates.