So I've had this problem for awhile (well over a year), and I just now noticed it only affects this website.
Occasionally, if I leave a tab open, right click stops opening the right click menue. I figured it was just the tab being goofy, but I just realized if I go to a different website, I can right click there, but if I come back to the forum the right-click menu still won't load. The problem is localized to individual tabs, so going to an unaffected tab, or opening a fresh one, fixes the issue, but I figured I'd mention this to see if anyone else is getting this issue, or if it's just something dumb on my setup. It's been bugging me for awhile since I use right-clicking a lot to open quotes in new windows rather losing my place in a thread.