I've had the Samsung G810 for a few months now and experienced the same issue. As it turns out, I finally got it to work by being patient. Apparently, small devices with GPS chips in them take a while to fixate on the satellites. Its common from what I see in various forums. I finally got it to work. I downloaded google maps for the G810 by going to google.com/gmm on the phone's browser. After running google maps (which supports the assisted-gps the phone is capable of), it finally found and kept the signal. This can take one-five minutes or more. I get mine to work about 70% of the time now. It can be quite frustrating though when you need a signal instantly. Hope this helps
