Delete all osbot files, you can keep your scripts, just temporarily save it somewhere else. Then, if you don't already have the highest version of Java, I recommend downloading it because it will help solve lots of other errors that can possibly occur. Then re-download the client and check for any errors. If same error occurs, I'd recommend getting intact with some moderators, giving a little info about your computer (32bit, windows, etc) and waiting for the next version to come out.