Dropdown list data submition to SQL 2005 error

Hi,
This is my setup. Three tables related, one web form where i input my selection then submit to a storeproc for the insert into SQL.  When I submit i get the error that it could not convert a nvarchar to integer. There is no problems if I only submit textbox values, the problem is with the dropdown lists which are bound to a data source and when i submit the datavaluefield I get the error.

Tables
Catagories                  PartType                  Reportable              Parts
*CatID                       *PartTypeID             *ReportID  &nb ...