Ok, reinstall Flash. Also, make sure your ports are open. Specifically 5222 and 5229 on of1.kongregate.com. Also check if the problem appears in another browser.
It depends on your browser. This thread has the method for clearing the cache for the 2 most used browsers, Internet Explorer and Firefox. If you are using another one, tell me and I’ll tell you how to clear the cache.
 "Notverygood"){kind=small}
 "Razzi3l"){kind=small}