Just wondered if anyone has seen this or knows what might have caused it.

On my rear wheel there are cracks on the rim where the nipple hooks into the rim on 7 out of the 10 drive side spokes. One nipple has almost pulled through the rim completely. There have been no crashes or major road obstructions hit. Plus, it seems like it must be structural as it has only happened on the drive side. Any ideas?

over tightened spokes ?

It's time for a new rim. The drive side spokes are tighter than the left side because of the dishing. It sounds like they have been overtightened.

Well, it's definitely time for a new rim (actually a new pair of wheels). I don't think it's overly tightened spokes as I've had some that were too loose. At this point the rear wheel is so messed up there's not much I can do with it anyway. I think I will contact the company to see what their warranty policy is and if this is a problem they've had with these wheels before.