i have the same problem.
work when you attach an external antenna.
the problen is the antenna module, it needs replacement.
I have not been able to find this part online. Maybe Garmin will sell it. Otherwise they will fix your unit for $200 but ts cheaper to get another one for $136. so the delemma continues. the external antenna from Glisson works its only $30, garmin also sells one for about the same $$$. I'm thinking if i can't find the part, maybe i can get it from the external antenna, hopefully it will fit. There are instruction out there on how to take apart the nuvi 360 so you can change battery display etc... I've taken my unit apart, thought it may have been the twisted circuit board that developed a bad connection from fliping the antenna, but it wasn't the problem, I just think the antenna module goes bad after time
me, May 2009