How can I fix a file with unreadable content?

I have a file that I've been using for years and recently my Office was upgraded from 2007 to 2010 and this is the first time I've started using this file and I started getting an error when attempting to open the file (see error below). The file is in .xlsm. When I attempt to open it, it says, "Excel found unreadable content in.." and I am able to recover the file; however, I CANNOT save the file or even save as a different filename or format, like .xlsx.

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Is there any way to fix this?

Thanks.