My money is on interference, but also the battery could be an issue.
This is what happened to me:
I had this issue for the longest time.
I decided to get my battery checked since it was winter and 4+ years old. Anyways, while the car would turn over fine, the battery tester said it was a bad battery, so I decided to get a new battery.
With the new battery my remote works just fine again, however, at the parking lot of the gym I go to, it has the hardest time working. My money is on interference. As someone mentioned, maybe its a CCtv thing...the lot I park at is shared with a bank, so I wouldn't be surprised if there are video cameras all over the place.