I've seen this a couple of times, playing a game against the AI (Professor) where the worm is not moving, but making noise as if it is walking or jumping. I believe this was both on regular land and land that has been effected by a weapon. The AI worm would make noise like it was walking and jumping, yet be stationary. Then, it would finally start moving and the sounds lined up just fine. Seems like it was not a case of rubberbanding or some sort of lag, but just like it was stuck.

edit: ver 0.0.130 : 03/09/2012

Thanks Wormplayer. We're looking into this.