http://en.wikipedia.org/wiki/CacheCache files keep temporary data, for example thumbnails images, so they do not have to be loaded everytime. By clearing your cache once, this allows a clean palate for AM to work with. You don't have to clear them everytime but I have found clearing them after placing any new modifications to TS3 (i.e, custom skins or texture replacements will need you to clear the cache once or twice to take effect) fixes potential problems. Loading menus might be a bit slower after clearing cache because it has to recreate them. After that all should be well.