Unable to edit/delete classes in AOT - AX3 SP3

[ginmur]

I have a strange problem with AOT. Suddenly (maybe after my programming lessons) it is somehow "locked". I'm not able to edit classes in AOT. I can however edit reports.
But when I edit a class, save the changes, then during debug I see the old code. When opening the metod for editing, the new code is there. But when restarting AX, the changes disapear.
Also I;m not possible to delete any of the method.

The changes are in usr layer, I;m logged into usr layer.
I already compiled AOT, deleted aoi file, nothing helped.

Any ideas?