Ahhh! So Firefox can get through Lon's barrier! Well, he's able to barricade himself against Safari, cuz I can't cut=and-paste either... Thanks ever so much for posting it for us, Castle.
I just tested it. It's the script blocker. Unlike IE, you are able to select and highlight the text in firefox whether scripts are blocked or not, but you can only right-click to copy if scripts are blocked. If they are not, you can still highlight and do a ctrl+C and get the text that way.
The script blocker I use is an add-on called no-script, and you get it just like you get any other FF add-on.
Of course, if you are a regular poster on STards, you'll need to toggle scripts on and off, or else it probably won't let you post. No-script is good at that, since there is an option box in the lower right corner, that you can click to allow or forbid a website.
Even if dicking around with an add-on is too much work, you at least have a workaround with FF, via ctrl+C or the edit menu.
Gotta love mozilla.