Heard on the tele that Frenchman Thomas Levet had to change his 5-iron as the 3rd groove up didn't conform to the new v-groove standard as laid down by the PGA.
It seems they did a spot check at the tournament in Morocco.

He went on to change his 3, 4 and 5 irons so that he didn't just have one odd club.

It did make me wonder what happens if you play with a damaged club of sorts, maybe one that has a big stone chip in an individual groove... ilegal?