Comment 39 for bug 65609

I had the same installLocation problem, unable to install new extensions, and removing my extensions.rdf fixed the problem.

Oddly enough, I noticed a side effect: switching the UI from English to German.
I installed Ubuntu in German but for some reason Firefox was in English, maybe because the profile comes from a distro that I installed in English .

Here is the chronology of what I did :
1) Ubuntu in German, Firefox in English
2) I try to install an add-on https://addons.mozilla.org/en-US/firefox/addon/1916
3) I get the installLocation error
4) I look up and find the trick on this page
5) I close Firefox
6) I delete extensions.rdf
7) I restart Firefox
8) I install the add-on successfully
9) I restart Firefox
10) I notice that Firefox's menus look a bit unfamiliar. Indeed, they are in German instead of English

I don't mind having Firefox in German, it's better, but I find it surprising, maybe the removal trick has some side effects.