My buddy has a jailbroken iPhone 3G with 2.1 and his MobilePhone.app continuously crashes when he opens it. It seemed like the permissions were somehow set wrong but they weren't. Just in case, I re-set them and applied them recursively. I also replaced his MobilePhone.app folder with the MobilePhone.app folder from my jailbroken 3G 2.1. His phone's been jailbroken for a few weeks and this has only started recently. Nothing else has really been changed other than downloading a few apps from Cydia (that I also have).

Does anybody have any other ideas? We'd like to leave Restore as a last resort.