I did all that. Still got the error. What I found was this: UserPreferences.ini file (which should be located in your Documents\The Lord Of The Rings Online folder) under the section [Net] and look for the line:

ComputeUniquePort=True

Change True to False.

You still have to have them start from different folders. However, as of today, you can start them separately now. Tomorrow "Mines of Moria" is released. I hope it still works.