Hi Andrew,
This may be a result of the soils database not being populated. From the layers in your table of contents, it looks like you may have used the Web Soil Survey to download SSURGO soils (the prj_soilmu_a_aoi layer). In the zip file you downloaded, there should be a soildb_US_2003.mdb file in addition tot he spatial, tabular, and thematic folders- the soildb_US_2003.mdb is just an empty template that needs to be populated with the data in the tabular folder. If you open it with Access, you can then use the Import macro or Import form to populate the database. When you open the database in Access, you'll have to click Stop All Macros, then click Enable Content in the Security Warning banner before you can run the Import Macro. Once you've imported the tabular data into the database, create a new parameterization and then a new simulation and see if the problem is fixed.
Shea