i have tried several times to install the Firefox sync add-on. it goes through the install process but then i get this message: https:// addons.mozilla.org/en-US/firefox/downloads/latest/10868 addon-10868-latest.xpi?src=/addondetail because: Invalid file hash (possible download corruption-261 i tried restarting my computer and installing again with same result. == i tried to install the sync add-on