In sci.space.shuttle Jim Oberg wrote:
I recall that there's been at least one actual
shuttle launch where a low-level sensor triggered
shutdown earlier than scheduled -- but nobody seems
to have any record of this at NASA. Does anyone
else recall which flight this was?

I'm not sure what the reason was, but 51-F, Challenger's last successful
mission had a premature engine shutdown resulting in an ATO. The mission was
still able to be carried out in the lower orbit.

http://www-pao.ksc.nasa.gov/kscpao/chron/sts51-f.htm