This is driving me crazy!

When trying to get a median in column by roll up, I keep getting the following error message immediately after attempting the roll up:

This does not happen when I do the same thing for other counties. It is very frustrating. I have tried re-downloading, and have updated the information. I even tried renaming the file. Anything related to this county has the same problem. There are no empty cells in the data. I need to get my work done!!! This is the feature that got me to purchase the software.
Thanks for any help,
alhaas