We just encountered the same problem, although it was silent ans we didn't notice for a while.
This is probably probably because an IStream on compound file implementation of streams does not support opening streams in transacted mode. SolidWorks 2015 changed their IStream to throw a NotImplementedException in Commit().
The MSDN documentation is vague as to what Commit should do in this situation. So throwing an exception and being silent are both "correct", except that changing the behavior from the latter to the former breaks the code of anyone using SolidWorks 3rd party storage!
If your code is general purpose, the solution is to wrap your calls to Commit() and Revert() in a try catch block and silently eat the exception and move on.
If your code is SolidWorks specific, then simply remove the calls to Commit() and Revert() since they do nothing here.
Thanks Serge. That turned out to be the right answer!