According to Smoking Gun, the indictment mentions a 3 year statute of limitations. The check in question was written on 9/13/02, and the indictment is dated exactly 3 years later. Apparently, Earle waited until the last moment to file the indictment in order to gain the most political advantage for the 2006 elections and to pile more crap on the Republicans at a time when the media is criticizing them for the hurricanes.
It wouldn't have mattered. DeLay announced earlier this year that he would waive the statute of limitations in any case, in order to clear himself.