The shock charge follows a skirmish in the game at the Abbey Stadium, which saw U's player Warren Goodhind red carded for an elbow on Iron striker Steve Torpey.
Goodhind's card, and the automatic three-match ban, were rescinded on appeal but both clubs have now been stung by a charge.
It is alleged that Torpey was involved in an incident after the card was shown, and faces a three-match ban if found guilty.
Iron boss Brian Laws told the Scunthorpe Telegraph: "It's come as a surprise to everyone at the club, as far as I am concerned there wasn't a mass brawl or anything of the sort and that is quite clearly shown on the video.
"We were awarded a free-kick after the sending off and five or six players went in there to calm things down and separate people before anything could happen."
United face the same charge last season following the Carling Cup game with Oldham Athletic.
The club successfully cleared their name, after being represented by former FA Compliance officer Graham Bean - who went on to lead a takeover bid later in the season.