My guess is that you are hand holding the camera and breaking the "rule" of having the shutter speed be 1/focal length in mm. Buildings tend not to move much so I think that it is the camera that is moving. Night images have less light and your camera will choose a higher ISO and slow shutter, long open duration, to compensate for the low light level. Getting a mono/tripod or, less expensively, setting the camera on a table or holding it against a wall will stabilize it and reduce or eliminate the blurring. If you are doing that already you may be pressing the shutter release button too hard/quickly. Look to see if mirror lockup or external flash are possible with your camera as they can be the cause of vibration even when using a tripod.
