gbillett,
I had some time to try and work on optimizing a factory profile, and found that the ColorMunki will not allow you to open a profile that it did not create.
When I tried to create a new one or optimize one that I had already created from the ColorMunki it was fine, but it would not open any profiles that were otherwise installed on my system. Prints are drying from my custom profiles and the factory one now so I'll let you know what I see tomorrow. I am testing Museo Silver Rag for this round.
Kevin