The dreaded "no more fonts" error

I have a workbook that makes use of the Bruin outlook macro that's full of dozens and dozens of hidden sheets, most roughly the same format.

I have NO charts in this workbook.

Some users (I distributed this for employees across my company intranet, they all use MSO 2010) receive the "no more fonts may be applied" error upon just opening the workbook, and some work just fine.

I suppose it's possible that I've exceeded the 4,000 font combination limitation but I highly doubt it. Regardless, I'm currently going through and trying to consolidate font combinations.

Is there a reason some users would be getting this error while others (including myself) don't? I had the user close all other workbooks before they opened mine and they still got the error.

Sorry, but as I said I have NO charts in this workbook.