Do you have any specific frequencies programmed in? When I got my 310 it didn't pick up anything at first. After I programmed in some frequencies, the open searching seemed to work much better for some reason.
I have a 600 not a 500. However, I made this stupid error once. Do you happen to have your USB cable connected to your external port? I was uploading from ARC and forgot to remove the cable from my external port. Just a shot in the dare.