I also have a D90 with a faulty GPS port. And, like you searched the net about this failure and agree it seems to be a common problem. I contacted Nikon support as well as the head of customer service. Nikon denies a problem, hiding behind the belief that since Nikon has not published a service bulletin, therefore no common problem exists. Needless to say, I found their response to be shallow. It's like an ostrich putting its head in the sand and pretending danger is not present.
As I understand it, the main circuit board contains the GPS port as an "appendage" and needs to be replaced. The estimates from a well regarded Nikon authorized repair shop and local repair shops are all in the range of $275-$300.
Perhaps Nikon needs to hear from all owners of Nikon cameras that have faulty GPS ports.