Try without the addons, at first?
Under the Firefox menu is a Help item,
One of the entries is "restart without addons"
Default settings can be achieved by a new profile, close firefox and run
Code:
firefox --ProfileManager
or alternatively,
Code:
rm -fr ~/.mozilla/firefox/
or less destructively,
Code:
mv ~/.mozilla/firefox/ ~/.mozilla/firefox.backup/
and fire up firefox.
NOTE: If you rm or mv ,
Code:
firefox --ProfileManager
becomes unnecessary.
Does Shift+F10 activate the right-click context menu in Firefox presently?