Seems like this only happens on ICS and an Android phone. I'll ask the dev team to review this since I don't have an ICS phone.

..or maybe I should finally root my LG Optimus 2X and install ICS.

Maybe it's some issue with the custom ROM, it works fine on stock ICS for me. You should be able to enter the lock screen with the app in the foreground; locking your device should not crash the app,...

Are you on Wi-Fi, 3G, or both when this happens? Have you noticed the app crashing without the SGS2 being locked?

If you haven't already, try these general troubleshooting steps individually and...

Is this happening consistently or intermittently? If intermittently, how frequent is it?

This doesn't seem to be a problem on my Asus Transformer Prime both with slide unlock and a pin. But it's...