dstiles - 7:05 pm on Apr 3, 2013 (gmt 0)
Thanks. I've monitored various Mint (and Ubuntu) forums but nothing useful so far. A lot of the stuff I've seen on the topic applies to Cinnamon and xfre (sp?) and has no relevance to Mate. I'll try, though.
I solved the tab-mix-plus problem by installing the latest version - I had a stop-gap beta version, installed to fix an annoying problem. Strange, though: this copy of Firefox does not show tab-mix-plus in add-ons search. I had to go to the site for it.