The maximum shutter speed I'm able to set my D600 to is 200. Can someone help me figure out why? I am NOT using a flash attachment so I'm not sure what the probem is.
Is the pop-up flash down securely? I would try putting it up and then back down again. The only other thing I can think of is that the camera is setting the SS and you are not directly in control of it... i.e. aperture priority with auto ISO or some program mode.
DSLR cameras often have a switch on the hot shoe to detect if a flash is attached. If the switch sticks in the flash attached position, then the camera might limit the shutter speed to the sync speed.