I have been having the same problem for over 2 weeks now. Everytime I log in I am immediately logged out by the system. I have tried repeatedly clearing my cache, deleting internet temp files and cookies, uninstall/reinstall SL, rebooting, logging in to different (quiet) regions and nothing works. I have been able to log in with a different account with no problems. I have reported this to SL Support with no help or solution so far. I read somewhere on this site that the issue may be caused by an avvie being "hung up" in a region and will continue until that region is restarted. But surely if that is the case it would have been cleared up after 2 weeks.