I just had the same problem and found a solution on another thread on this site. Clean the screen really well with Windex and dry it. Check all 4 edges for crumbs that might be lodged in there. I found one tiny crumb. I dislodged with a small nail file (gently!), wiped the screen off and then it worked! I didn't even bother recalibrating it. When I turned it on and went to the sign in screen, it was working fine. The original post also said to try "milking" the screen in case pressure had caused it to stick. Press gently with your thumb on the screen in various spots around the screen, then try again.

Capnsven - thank you so much! My daughter has only had her Leapster 2 for about a month now and it stopped working! It would start up and get to the sign in screen and then it wouldn't do anything. I cleaned the screen really well and found ONE little crumb stuck in the side of the screen, got it out and it works now! Thank you thank you! I almost went and bought a new one!