Guys, we've run into the same issue as well. A reboot of the Aruba controller would fix the issue temporarily. We were experiencing the authentication issue about once a week. A user would come onto campus, and never get out of the initial role (registration) even though their device was registered in Bradford.
I spent hours on the phone with Aruba, to no avail. we upgraded our controllers from 6.1.3.6-airgroup to 6.3.1.6. The issue was still occurring.
After calling Bradford back for a second time (the first time they said they didn't see anything wrong and that it was an Aruba issue) they noticed a bunch of SSH authentication errors coming from Aruba. Aruba was having issues logging in.
At the time we were running Bradford NS 6.0.x. We upgraded to Bradford 6.2.3.98 and the issue seems to be resolved. It's been a full week without a problem.
I hope this helps.