I had pretty bad reception problems with my '500. FWIW, here's what happened with me. I'm not posting this to trash GRE, its just a condensed version of my experience trying to get my PSR-500 fixed.
I was one of the first to get a PSR-500 last year when they came out. After about 5 months of use, I had a problem with my PSR-500 where it would not receive anything, and I mean anything at all. When I pressed the WX button to pick up the National Weather Service, it would not pick up the local transmitter, even when I was driving by it!
Let me say that I try to take very good care of my electronics. I did drop my '500 once on accident, however it worked fine after that and the reception issue didn't start until months after the drop occurred.
I sent my '500 back to GRE last May. I did have the infamous loose screw. The replaced the BNC connector and it worked fine for a couple of months. Then, i'd loose reception again. However, I noticed I could get reception to return by pressing on a spot on the case between the LCD and speaker.
I sent by '500 back in September for the same issue after having this problem again. Again, the BNC connector was replaced, and I was blamed by letter for breaking the BNC connector by using an external antenna! They sent the BNC back to me, and besides the damage that occurred during replacement and some minor corrosion, it looked ok to me. Honestly, I was at a loss to explain how the BNC connector was causing this problem. BTW, they never bothered to ask me how I had my mobile setup and the strain relief I had built in.....
After I got my '500 back, I didn't use an external antenna (only the RS 800Mhz antenna that GRE makes for RS) and the disappearing reception problem occurred again within one week. Again, I opened a ticket and sent the '500 back to GRE, and I even included a Quicktime video that I shot that showed the problem. This time, GRE replaced the PC boards, and so far it appears to be working fine. I really, really, really hope that the problem is gone, since its out of warranty now.
I suspect I had a problem with a bad ribbon cable, bad connector or cold soldered joint. It acted like something was shorting out internally. When I first reported my problem, a GRE representative called me on the phone to find out more information and he did admit that they had been experiencing quality control issues with the early production units.
Warren