Have you tried clearing your browsing cache to see if that helps? Here is a link that shows you how to do so on firefox.
If you're getting the issue on just a few select problems, please let me know which tactics they are and I'd be happy to test it.
Frequently, when I solve a problem in TT then the thing freezes and doesn't continue. It's frustrating to not get the points when the solution is correct. Does it have something to do with my browser. I use Firefox, or is it the site?