I saw a very similar bug with my Motorola Cliq (which eventually, half-heartedly got updates) using the stock T-Mobile ROMs and Cyanogen Mod. Though I didn't t

I saw a very similar bug with my Motorola Cliq (which eventually, half-heartedly got updates) using the stock T-Mobile ROMs and Cyanogen Mod. Though I didn't track it down to that specific case I actually tended to use it while charging pretty heavily. Not sure if they're using the same hardware for part of the touchscreen, the S definitely had higher-end hw in general.