Hi. I have a 2011 15 inch MacBook Pro. I've noticed my screen will literally lock up.. I can move the cursor, but I can't click on anything, and the only way to make my system responsive again is to do a hard reboot. I'll have what looks like stuck pixels or something on my screen as well.. I'm not even doing anything that's demanding a lot out of my machine. Sometimes I can just be sitting there on IRC with only one or two other apps open and it will lock up, and sometimes I'll be waking my computer from sleep and it will lock up. I can't reproduce this problem, sometimes it will happen maybe once every 2 days, sometimes once every week, but it's enough to make it annoying. Any help would be greatly appreciated! Thanks.