Might conflict with Tab Mix Plus Rated 4 out of 5 stars
It doesn't work for me and I suspect it is because of conflicting with Tab Mix Plus where you can also configure some combination of key to perform certain task.
In addition, the "Open tab in Google Chrome" doesn't work. Notr sure is it the same cause.
I fixed an issue reported by another user, who had symptoms sounding exactly like yours. Please let me know if the latest version solves your problem: https://addons.mozilla.org/firefox/downloads/file/152768/open_in_chrome-1.3.5-fx.xpi
Note: The addon has been tested with with Tab Mix Plus and does in no way conflict or interfere / get interfered by that addon, if anyone else is wondering or is concerned about the claim.
Please let me know if the fix included in the v1.3.5 also solves your problem.