Since I thought you just switched from Nuevasync to erminig I thought it would just work. Well, it's not so easy.
I manually deleted all the duplicate and triplicate entry at my google calendar, and after that I found that nuevasync did not synchronize any longer.
I think promotion to Extras-testing should come with appropriate warnings of 1) to back up all local and remote calendars and 2) to start with empty calendars in the N900.