This error can occur if complicated queries are used in the appeal mailing. You can make the queries static and the appeal mailing process will run normally.

Here are the steps: 
  1. Go to Analysis > Information Library and make copies of the queries used in the appeal mailing. On the Set Save Options tab, mark the options to Create a selection and Create a static selection. 
  2. Go to your Marketing and Communications > Appeal Mailings and copy your mailing. 
  3. In the copy of the appeal mailing, replace your dynamic queries with the static copies. 
  4. You should now be able to update count and run the appeal mailing successfully.