The only thing you can really do is run on OpenJK, you can do it through the launcher. I'm still adamant on figuring out what fixes it though. What graphics drivers do you have?
You could try what @ent suggested, I had no luck with it.
The UI and chat boxes are too big for my taste. And OpenJK has its share of bugs to go along with it. (Though that department has been improved I can say that)
I've been trying to figure out what is causing this on my machine when I run MB2 on JAMP. This does not occur on OpenJk (But I want to try out all my options before I switch over, it just isn't the same.)
After verifying my files and testing again, I achieve the same results. Every time I join...