The CRC has put forth a letter from the AKO (associations of Kashrus Organizations) that they are concerned with the kashrus on certain brands of whiskey. This kashrus concern has nothing to do with the ingredients but rather the ownership of the companies. If the owner of the company is Jewish and did not sell his chametz, then the reasoning goes the whiskey becomes chametz she'aver alav pesach ( was owned by a Jew over the passover holiday) and is therefore forbidden. None of the other major Kashrus organizations have jumped on this bandwagon and it remains to be seen if any will. You can view a copy of this letter here.