Look at the sticky for common problems.
After spending a long time reading it, I'll try to clarify one point for you. There are two common problems that are slightly different. The defective part might be the antenna, and it might be the switch.
Study your car's behavior closely. When you pull the handle, does the car do absolutely nothing, or does it flash red to show you it's denying entry? The former indicates switch, the latter indicates antenna.
Said differently, the bad antenna behavior is the same as if your fob isn't with you. It knows you're trying to get in and denies the request. The bad switch behavior is the same as if you never pulled the handle at all.
Either way, the permanent fix requires replacing parts. If it's the switch, you can try spraying contact cleaner or WD-40 blindly into the handle. That worked for me, but I don't have confidence that it's going to be permanent. It's only been a week.
The sticky thread above on page 6 links to a nice how-to from Neutrocuted with photos.