Incredible shrinking then disappearing command button captions???

I just noticed something that is weird, with the actual command button captions on my Excel spreadsheet. Every time I clicked this command button, the caption shrinks and now is basically disappeared. I checked the properties and it does show "GENERATE PO (.xls)", which is the caption in that field, and the Font = Arial, 16 pitch, Bold, Visible = True, Forecolor is = black, but is no longer showing up on the command button--its disappeared. Has anyone heard of anything like this?

After creating a thread just now named "The Incredible Shrinking Option Button Label," I discovered yours. Did you ever find an explanation / solution?