Thank you Richie(UK) and Helmekki,
The workbook was digitally signed by me on the Office 2K machine that I no longer have access to.
The workbook was not set up as being a shared workbook.
However, I did make it into a shared workbook. I received an error stating that I couldn't share it because it contained macros. Clicking the OK button saves the workbook anyway.
I then removed the Share (that it alledgedly couldn't have) and sure enough I can View, Edit and Step into it's macros.
Thank you very much.