To fix this problem, head to your steam folder and delete the folder called "userdata". In my personal case, that can be found at: C:\Program Files (x86)\Steam\userdata Delete the "userdata" folder, restart steam, and you should no longer have problems joining servers. You'll be required to re-enter the account protection code which they'll send to your email address. Thanks go to complete_lamer and Ducky for searching around and finding this solution. EDIT: It seems an easier solution is to delete the file in Steam\config\config.vdf You may have to re-enter the steam verification on restart but other than that, it should work fine. EDIT2: Siro also reported that deleting userdata/[number related to account]/config/localconfig.vdf will also work, but won't force you to re-enter the verification code on restart. Use whichever method you want. EDIT3 01/01/2013: Seems the problem might be back, but in a different capacity. The old "delete clientregistry.blob and restart steam" trick seems to work for this one.