Sorry to hear of the problem with your D300. First as Leo recommended, I would check the electrical contacts on the camera body and the lenses. Make sure all of the electrical contacts on the lenses are projecting out the same distance. They are spring loaded and can get jammed in, that could cause the problem.
According to the Nikon USA site, there are No Nikon Authorized Repair Stations in St. Pertersburg FL. If the contacts look ok and using DeOxit doesn't solve the problem, Nikon Service in Melville NY should be able to get it fixed.