I suspect it happened on my last commute to and from work on Tuesday. I just had a broken spoke replaced and the wheel trued about two weeks ago, it is the original wheel and the bike is a 2001 model. It looks like the crack originated from stress at one of the spokes but this is just speculation, weird thing is the tire does'nt seem to be losing any air but I know not to ride the bike until the wheel is replaced. Sorry for the crappy iPhone pic...