This is really weird. I had the same problem with a number of car chargers. Whether they would work or not seemed to be a function of how much power the Evo was using. With google navigation turned on, it would not charge. I noticed that if I stressed the cord to the right (while looking at the phone, plug in bottom), it would charge properly. I attached a fat rubber-band via half-hitch to the cord right below the plug, and loop that over the right upper corner of the Evo. That stresses the plug in the mini-USB socket somehow and makes it work. Now I can use navigation on long trips in the car. I don't know what on earth HTC can have done to create such problems with simply plugging in a USB cable, but it is really true that the USB connection is problematic -- and not in any reasonably predictable way!