Sony nav-u NV-U70 Car GPS Receiver

My Nav-U seemed to work well when i fist got it. Im in the service industry and have to go to allot of addresses in South Florida.
As time went on Ive noticed more and more problems. I even found that if i enter an address in Miami Gardens that the unit crashes and has to be reset!
Most of the time it works well but when it doesn't it is a real time waister.
I baught the extended warranty at the sony store where the unit was purchased. However for them to do anything it has to be sent back to sony and tested by thier techs.When I shelled out $100 dollars for the replacement warranty they didnt mention that the SONY STYLE store in BOCA RATON Florida where it was baught did not honour the warranty.