BlackBerry 10 Dev Alpha phone's self-timer has gone off
Had there not been a delay, developers would have by now exchanged the Dev Alpha phone for a limited edition BlackBerry 10 handset. This would have taken place about a month prior to the consumer launch of the new platform. The launch was supposed to take place in October.
As far as the phone is concerned, if you reboot it a few times, the message will stop displaying. With the delay in the launch of BlackBerry 10, RIM will undoubtedly extend the internal clock a few extra months. In the meantime, just be glad that the phone didn't self-destruct when the clock hit zero.