alternative ways to unlock
i have had a problem with my pearl too where i couldnt unlock because the top media keys became unresponsive (which i still got to resolve) anyway, i found two ways on unlocking without doing a battery pull,
1, hold down the red power off key for a few seconds until the phone starts to shutdown. it gives you the option to press any key to abort and if you press any key, the phone will cancel the shutdown and return to the home screen
2, is to dial an emergency number (911, 999, 112) i suggest using one which is not for your country so you dont get through, as it dials, you must hang up before it rings and your phone will return to the home screen..
i hope these help.