Sorry I was a little quick to post this topic, I was running out the door.
I actually can't see a stack in the error I'm getting.. see the attached image
I don't know if this helps but here's what I get in the designer when after I place the SF Listbox and configure the SF:Item Population settings:
There was an error rendering the control.
'GKG.CompanyPromo.BusinessObjects.AdonixRegionBO|FillAll;|zregion_0,|{0}|zregion_0' count not be set on property 'PopulationDataSourceSettings'.