Called about this today. I was directed by support to do the following:

1. Save the Other Income Worksheet generated by ProSeries that shows the K-1 income and information as a PDF.
2. Attach the PDF to the return using the EF Center.
3. In the "ProSeries Attach PDF Files" menu that you use to attach a PDF in the EF Center, be sure to select the option "Form 1120 L10" in the drop down list in the "Type" column.

I have not filed the return yet, but performing these steps removed the error from my return.

It seems redundant to have to attach a ProSeries worksheet to a ProSeries tax return but that is apparently the solution to this problem for now.

Hope this helps.