You couldn't just write "version 1.0.3" instead of the screenshot, lol? Anyway, that is very odd. I've never seen that before. But because I'm feeling helpful, I'll post this over at the vBulletin support forums and see if anyone over there knows what's going on.
EDIT: I've found a workaround. It isn't permanent, mind you, but it works. Use "Ctrl + V" instead of the Paste button up top. No error then. Believe it or not I receive the exact same error when clicking the Paste button. I'm on Linux, too, using the same version of Firefox.
EDIT #2: The kind folks on the vB support forums have posted a solution. Go here:
http://www.ipkonfig.com/cms/index.p...d=165&Itemid=29 Enter "about
:config" in your Firefox navigation window. That will pull up all the Firefox settings. Make the appropriate changes.
EDIT #3: While that guide gives you a wonderful speed increase, it doesn't solve the problem. I just posted that and hopefully we'll have a better answer soon.