Hi to all.
I`ve faced the same problem recently. Although this problem is claimed to be solved, I hope someone has found out, what caused it. If so, it would be great to know, what conclusion you came to. It would also be good to know, how to deal with this problem. Assuming that reinstalling Autodesk Material Library is not an option.
This exception occurs only within next configuration: Revit 2015 on virtual machine with Windows 7.
Thanks.