Conquest of the Horde

If you purchase any of the riding skills and they do not show up immediately, log out and back in. This appears to fix the problem.

I had noticed last night that it seemed to... 'miss' me getting 300 skill. Unfortunately, I didn't try to relog, and instead fixed the skill manually. However, while I was doing so, I also noticed that trying to just set my skill to 300/300 didn't change the bar from 225/225. I had to unlearn it and then relearn it. This leads me to believe that it is indeed just a 'delayed appearance' sort of bug client-side, as you say.