After Iowa "scored" to make the game 20-3 Iowa, Tate gave the "horns down". The play was called back and he threw an interception on the next play. From that point on Texas outscored Iowa 23-10.
Shawn Bell Gave the "horns down" when Baylor went up 7 -0 but they ended up losing 63-31 (I think) two weeks later he hurt his knee and was out for the season.
In 2003 Arkansas Coach Houston Nutt Gave the "horns down" and Arkansas lost 3 of thier next 5 games. The next season The lost to Texas at home and went 5-6.
It seems the "horns down" sign has a pretty decent karmic payback.