I just had this happen to me. I was not cc'd. At the time I was farming top lane and switched from hammer to cannon. I probably used my e to create a gate while the transformation was going (i say probably because i frequently use the e+q combo to farm caster waves, but i was just going on automatic so i am not sure), after that I could use my e in cannon form and my w in both forms, but i could not auto attack or use any offensive spells. I tried changing stances to reset it but that did not work initially, i then logged of and back on and that also did not work, i then restarted my computer and that did not fix it, after running around for a while and changing stances the problem seemed to fix itself. I was using the fullmetal jayce skin. I have been playing him since he came out and this is the first time i have had this issue, but as it cost me a ranked game i was rather upset about it. I don't know how common the issue is but it was rather frustrating to me.
After reading other people's posts about using to the skies i remember that i used it immediatly when the bug was fixed, i am not sure whether i used it before or after everything started working again but i cleared wraiths when my skills worked and i believe i initially jumped on them with to the skies.