Yep. +1 frequency. It's not like I was running an old version of FF with XUL extensions or anything like that, either - latest version, addons properly signed,

Yep. +1 frequency. It's not like I was running an old version of FF with XUL extensions or anything like that, either - latest version, addons properly signed, all added from Mozilla site. On top of that, attempts to re-add extensions via https://addons.mozilla.org https://addons.mozilla.org result in "Download failed. Please check your connection." errors. This makes me suspect that there's something up with Mozilla inf. There are definitely some good arguments in favor of Mozilla-signed addons, but events like this that expose an (apparent) SPoF are less than great. If only running one of the Firefox forks didn't involve getting security patches late...