When you expand a node with ServerSideCallback it works the first times. But if I refresh the page and try to expand the node once more, it hangs forever. Clicking it mulitple times just adds the loading symbol several times. This only happens in Firefox. I've tried both FF 3.0 and 3.5 and have the same problem.
I've managed to reproduce this on the demo pages as well.
Check this screenshot too see the problem.
Anyone have an idea where to start searching for a solution?