User Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:33.0) Gecko/20100101 Firefox/33.0 (Beta/Release) Build ID: 20140627030212 Steps to reproduce: the problem when E10S is enabled now is you can not switch between "Ask to activate, Always activate, never activate" or "check for update, view recent update...." in the about:addons tab!!
I had an issue like this once (except it happened even without e10s) and it was related to some about:config changes. Resetting your about:config should work.
I confirm! this resolved for me