Have twice in last month found Excel getting into a state where it refuses to save, returning the "Document not Saved" pop-up, after having successfully been through some code.

Most online searches on that "Document not Saved" text return information about issues accessing the target save location, so not code related. Those can be dealt with. More of an issue is where Excel itself gets into a state where it can't save. This thread is for folks to list any such they've found; preferably with 'solutions' where appropriate. I'll add the 2 cases I've come across as responses.