I’ve installed version 2.73, which should fix the Firefox problem. There are also many other unrelated changes – see the readme.txt in the plugin directory for details.
I tested forcing auto-updates, but unfortunately it seemed to work normally. Please leave it on manual update for a while, and let’s see if the same thing happens when you manually update from the ‘plugins’ screen. If it does, we can narrow down the exact steps to reproduce it – and then fix it.
Please let me know how 2.73 works for you, and if everything looks good I’ll publish it so it can be installed on your other site(s).