From ESPN:
South Carolina coach Shane Beamer needed to be restrained from pursuing Illinois coach Bret Bielema during a stoppage in the third quarter after Bielema came toward South Carolina's sideline with his arms extended, a signal to them that he was not happy with a signal given earlier in the game.
Beamer and Beielema confirmed the dispute was over a signal South Carolina's kick returners gave on a third-quarter kickoff when a player gave the typical signal they would let the ball go over their head and not return the ball. But the Gamecocks not only fielded the kick, but tried a lateral play that ended with a tackle at the 25.
Beamer said he cleared the use of that signal with the Big 12 officiating crew before the game and that it was legal, as long as the returners did not wave their arms like a fair catch. Bielema agreed that returning the kick was not against the rules, but went against the spirit of using that signal to limit injuries on kickoff returns