I seem to remember a game against Arsenal in the early 90s where the crowd announced was 25k or something.
Actually just checked, and it was the 0-0 on 23rd December 1990. Crowd given was 22,687, even though Villa Park was clearly about 90% full.
EDIT - Actually, I think it was the one the following season when we beat them 3-1 in August. Announced crowd was 29k, when the ground was pretty much full so at least 39k in. Crowds announced for both were at least 10k below the actual number in the ground.