I had a similar problem with my 0.5.1 client wich I used for a long time and wich had many maps, skins and other stuff (like the nodes and teecomp client I installed days before to try them) in it. But the problem appeared suddenly and existed only on some servers that worked days before very well. And i was the only one with that problem on those servers. I could fix it with a reinstall of the version 0.5.2 of the client and by killing the config teeworlds folder in my user directory. So the things Lanta said weren't the problem.
First i would check the things Lanta said. If it doesn't help then answer the question: How did you reinstall it? Have you deleted the teeworlds and the config folder before?
Edit: The title wasn't a good choice, because nobody know what the problem is. That you need help is clear because you post in the Support forum.