Turn off your phone and remove the battery and memory card. Wait for 30 seconds before putting back the battery and turning on your phone. Just keep on repeating the process until you get lucky. There is no assurance but it's worth a try.
This looks like a common issue with the LG Rumor 2 as there are many users having the same problem. If you just bought the phone, try asking for a replacement. If not, contact LG to find out where you can send it for repair.