If you get the Invalid Packet 13 error it means your phones firmware is not compatible with Msnap.
You can remap a key on your phone keypad to take screenshots (Seem 005B_0001 & set the value to FF) Here if you scroll down you can locate the Offset value of the key you wish to remap. You need to locate the offset value in XVI32 & set it's value to FF
Make sure to have a backup of your seem before editing it.