Rebooted? how? Pull the battery and do a clean reset. Also did you add any Apps ? That may be the issue. If this was the first time and does not return it may be ok. Generally that error is displayed because of a restriction on third party apps. Some companys do not allow this via the IT policy. You did not indicate if this is a corporate device. Also when an app is not allowed to operate and did not get the permission to run. This link may help
KB14726-Uncaught exception: java.lang.error is displayed when the BlackBerry smartphone is reset