In addition to the incidents listed in @PearsonArtPhoto's answer:
During the STS-115 launch countdown a wind direction change occurred at ~15,000 feet (15 ft/s tailwind to 10 ft/s headwind) over a period of roughly an hour. Since the first stage trajectory had been designed using the original winds, this resulted in a reduction in dynamic pressure margin. A special assessment was done using the L-1:10 winds measurement and dynamic pressure was predicted to be at ~100.2% of the limit where 100.5% would have been a "no-go" call. None of the "wind change" rules had been violated. This analysis took place between T-39 and T-28 minutes - per the normal ascent preparation timeline, the final assessment of this regime had already been done.
No limits were violated and none would have been if the issue hadn't been detected. Also, there was some amount of conservatism built into the system. But, we were ~0.3% away from launching into a possible structural loads exceedance.