Conversion from XWiki 1.0 to XWiki 2.0 failing on some documents

I'm getting the following error message when trying to converting some pages from XWiki 1.0 to XWiki 2.0 syntax. These pages originally come from Curriki. Apparently, all these pages come from Curriki user collections -> maybe there's an issue that's specific to them.

Failed to convert to the selected syntax. If you want to use this syntax anyway, you can select it again and choose not to perform the conversion.

When trying to convert a page (see attached XARs & log).