Hi all,
Just an update for future reference to anyone that will have the same problem.
Found the problem and it really was that the aes_busy was stuck on high in my design. The root cause for this in my case was that my implementation uses a reset input and I used usb_trigger as reset, which goes high when sending data (or something close to that) but my reset should be high for a single clock and not for the whole process of course. This problem caused aes_busy to stay high forever.
Thanks again for the help Jean-Pierre!
Ohad.