The shutter speed "X250" is at one extreme end of the available shutter speeds - it is actually beyond "Bulb" in the M (manual) mode, or beyond 30 sec in the S (shutter priority) mode. I've never used this setting myself, but it is apparently used to lock the camera on the maximum electronic flash sync speed in either M or S modes. Attempting to move the command wheel to the left has no effect because X250 is already at the end of the list. In M mode you should be able to move the command dial to the *right* and see Bulb, then 30" (30 sec), 25", 20", etc. The farther you move the command dial to the right the shorter the shutter speeds will become until, eventually, you reach 8000 (1/8000 sec) at the other extreme end of the shutter speed list. As already mentioned, you will not be able to move the shutter speeds to anything shorter than 250 (1/250 sec) if you have the internal flash raised - to reach 1/8000 you will have to put the flash down.
Does your camera behave as described above? If not, it sounds like you may have something that needs to be repaired.