OK, that,s the information I was looking for. What you have done so far is good but if you still can,t start/join a session go back to CM and see if you have any missing dependencies. If you have you need to find them one at a time and drag them to the download box. If you have no missing dependencies then the problem is locally modified assets. Again they need to be identified and deleted and when u have finished, download them again and check to see if you have got rid of all the modified assets. Rinse and repeat as they say.