@driedeker, I got that error message today, it appears CamBam is trying to open the theme file because it's extension is xml. Likely CamBam scans that folder for xml files and assumes they are all styles.
You solve one problem and create another.

I'll either have to use another folder or change the extension name.
Edit: new version attached to first post in this thread.
1. The theme file extension is now thxml (theme xml)
Please delete "CBTheme-Light Theme.xml" from the styles folder and start again with the new thxml file.
The main file called, "CamBamThemes.config" is okay and that should still be left in the styles folder.