That happened a handful of times on that CTS tour. At the end of that cycle and the two times I've seen them on this cycle they've been awesome and tightened up their vocals, which was the only thing lacking in their shows.
6/28 Meh-hem Fest
7/9-7/16 Van Halen :|
7/25 Alice in Chains?
9/29-30 Uncle Acid & The Deadbeats