With some threads like https://support.mozilla.com/en-US/questions/869069 and on mozillazine.
Apparently there is a incompatibility or conflict bug between Greasemonkey 0.9.10 and Tab Mix Plus.
An update to Greasemonkey 0.9.11 should fix it. https://addons.mozilla.org/en-US/firefox/addon/greasemonkey/versions/
http://tmp.garyr.net/forum/viewtopic.php?f=2&t=15046
http://tmp.garyr.net/forum/viewtopic.php?f=3&t=10888&start=2980
With some threads like https://support.mozilla.com/en-US/questions/869069 and on mozillazine.
Apparently there is a incompatibility or conflict bug between Greasemonkey 0.9.10 and Tab Mix Plus.
An update to Greasemonkey 0.9.11 should fix it. https://addons.mozilla.org/en-US/firefox/addon/greasemonkey/versions/
http://tmp.garyr.net/forum/viewtopic.php?f=2&t=15046
http://tmp.garyr.net/forum/viewtopic.php?f=3&t=10888&start=2980