Here's another fix that I've implemented:
1. Go to CVS or your local pharmacy and buy a roll of NexCare waterproof First Aid Tape. Buy Nexcare Absolute Waterproof Tape 1 Inch X 5 Yards online at CVS.com
2. Cut a very narrow strip (about 2-3mm wide) off the end.
3. Take off the battery cover. On the phone, between the memory card slot and the battery there's a narrow (2-3mm wide) indention that's about an inch long. (You see where this is going?)
4. Put your 1" x 2-3mm strip of foam first aid tape in that indention. Your battery door will fit snugly w/ little or no wiggle and the indention helps prevent the battery door from bulging up and causing gaps.