Excel gives error message when I try to save changes

I do have a work-around to solving your issue. HERE IS THE TEMPORARY FIX... Close the file and loose your changes you made (I know it sucks). Close anything in Excel you may have opened. Then while holding the cntrl button select the Excel Application and a box will pop up asking if you want to open in Safe Mode. Say Yes. This will disable macros but still allow you to have access to it. You won't need to access this most times this occurs and you can simply save the file. Close it and re-open it (not in safe mode) and the file works again. Maybe for a few days or months but it will probably happen again at some point without any reason as to why.