Hi Jocelyn, 

I created the new cluster using the "Add a New Cluster" option in the groups window. Duplicate cluster shows in 

1.jpg. shows the duplicate cluster
2.jpg shows the duplicate classes
3.jpg shows the ensuing compiler errors.

Murphy's law means that I can't reproduce the error. However, when trying to do so I found an error which I think is related: I can't delete any newly created clusters.

4.jpg shows the create new cluster window 
5.jpg shows the newly created cluster
6.jpg shows the delete warning (note the erroneous cluster description without separators)
7.jpg shows the cluster is still there, although I answered "Yes" 
8.jpg shows the crash when I close and re-open without the "clean" option

When I restart and open with the "clean" option set, everything compiles but the deleted cluster is still there. I can only get rid of it by deleting the folder in Windows explorer and restarting with the "clean" option

Hope this helps 
Martin