I too have observed this problem several times. For me, the problems occurs at every firefox upgrade.
It looks like a packaging problem.
When firefox is upgraded with apt-get, a firefox restart is required. But *between* the upgrade and the (firefox) restart, firefox behaves abnormally. It is not always practical to restart firefox immediately, e.g. the user might be writing an email or filling in a form. Errors include: assertion failed when a URL is entered in the URL bar, right click not giving context-sensitive menus (e.g. save image when over an image). Expected behaviour: Firefox should continue to work normally.
I too have observed this problem several times. For me, the problems occurs at every firefox upgrade.
It looks like a packaging problem.
When firefox is upgraded with apt-get, a firefox restart is required. But *between* the upgrade and the (firefox) restart, firefox behaves abnormally. It is not always practical to restart firefox immediately, e.g. the user might be writing an email or filling in a form. Errors include: assertion failed when a URL is entered in the URL bar, right click not giving context-sensitive menus (e.g. save image when over an image). Expected behaviour: Firefox should continue to work normally.
For further details see my bug report: /bugs.launchpad .net/ubuntu/ +source/ firefox/ +bug/365434
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