Twice in the last week LastPass has disappeared from my Firefox browser. Last Friday I was able to get it back with some difficulty. LastPass has disappeared again today (there was an update yesterday), and I CANNOT get it back now. I even completed removed the old version from my browser and tried to install it fresh from Mozilla's list of add-ons, but every time it tries to install I get message saying it could not be installed because Firefox could not modify the file. I don't want to switch permanently to Chrome, but I may have to.