Unable to save Excel workbook

[Sheridi]

I have at least 2 workbooks that I have been using for years. All of a sudden this morning, I am unable to save them. I get this message:

If I click "continue" and try to save to another location, this same message appears, and then I have to use Task Manage to shut down Excel. It is not happening with every workbook, strangely.

 

[Sheridi]

Should have checked for updates before I posted here. Updated Office (which I thought was automatic) and now no problems.

 

[Skyybot]

Have you tried the Open and Repair option?

 

[Sheridi]

I wanted to give it a few days to make sure the problem was corrected, and sure enough, it is back. Excel doesn't allow me to save the original, then asks if I want to save under another name, but does not allow me to save.