Firefox 15: Type error: Can't access dead object

I upgraded to Firefox 15 and got an annoying error:

I keep getting annoying often “Type error: Can’t access dead object” errors.

That message is displayed endlessly after using many web pages and closing their tab.

After some Googling I found page http://support.mozilla.org/en-US/questions/935811 that tells that Drag & Drop upload extension could be the cause.

Disabling Drag & Drop upload extension seemed to help.