GamePolitics reports that Valve has sued Activision Blizzard over underpayment of royalties. At issue is a royalty check for just under $2 million that was $424,136 shy of the $2,391,932 awarded to Valve by an arbitrator after a 2002 dispute with Sierra, which Activision claims settle past overpayments to Valve. Word is: "Against that backdrop, Activision cut Valve a check last week for $1,967,796 - the amount handed down by the arbitrator less the disputed $424K. According to Valve's suit, Activision said that it wouldn't pay the rest and if Valve went to court Activision would countersue. Valve has apparently called Activision's bluff and the parties are now once again at odds."