Comment 174 for bug 10910

The bug still exists in Thunderbird (not sure about Firefox). Every time Thunderbird is updated the paper size is changed to letter even if the user uses locale for which the right size is A4.

Check out this: http://ubuntuforums.org/showthread.php?t=889088&p=12423297#post12423297

Could it be the case that when Thunderbird update is installed, update process does not check at all what is 1) in the locale or 2) what value Thunderbird config variable print.postscript.paper_size has? This would explain the nasty behaviour.