I can't train with Gregori in the Arena...before being asked, actually I've got some training points, I've got some money...and I can train with all the others trainers...
In fact, when I click on "Train", the window with my skill opens, but the lists are all empty...so I can't choose anything...I assume this is some kind of a bug.

Another "bug" I found : I've just trained in order to improve my Strenght, so I've got some "Theorical knowledge". I'm going to the Arena, and I'm disconnected (Server crash I guess). And then, when I re-log, I found that almost my "Theorical Knowledge" has gone... (Hope that's really a bug, and not a "rule" I didn't know... )