I have never entered the actual Form 1098, I just enter the dollar figures directly onto Sch A on the lines where they go.
Sounds like a programming error. No one from INTUIT has posted that there is a fix or if this is a known error.
You would have to contact ProSeries to get this reported.
We are having the same issue. So far none of the clients with Mortgage Insurance Premiums are itemizing so I just delete their 1098 to remove the error.