Yeah but I can't think of many times they've had to actually pull a beta this late in the process. That a bug that big could make it through a month from launch is not a great sign. By now most of the big bugs should be worked out or at least well documented. They didn't even know it was in there!
Sigh. Relax. Things are working exactly how they should be working. Betas are TEST software. They know their are bugs and they use the user best to test and report on those bugs. In this case it was a Developer BETA - so they are using their most experienced users at testing and reporting bugs. Sometimes bugs are benign, sometimes more serious. In this case they found what they consider a serious bug before they released the BETA to the public. It's the natural workflow when creating software. It's not a bad sign at all. It's a great sign. Things are going exactly how they should. beta TEST!!! it's going to be ok.