This crashing to the desktop while trying to use the temporary ability bar only began in 1.9. I have never had any trouble with it prior to last night. I have done Rusilla and been the recipient of Dreadshot many times, and used the ability and not crashed. I even went so far as to disable 3rd party plugins like King Boss Mods, but it was simply 1.9 Rift being unstable. I have not had a chance to see if the crashing with temporary ability bar is soley Primal Feast or if it is the temporary ability bar everywhere.
Other team members seemed to be having issues too but just not as bad as mine. Wanted to bring it up in case this was a known issue.