Mate what server are you trying to join? Try installing or uninstalling Blockland Glass.
could be a corrupted cache, remove cache.db out of the folder (put it somewhere else) and run the launcher (or verify game files) - play some servers and see if it fixes the problem
Verify just makes sure you have all the correct files, that isn't reinstalling
Read that post wrong, but ya make sure you actually uninstalled and installed (back up your stuff..)