Could someone explain why calling Campaign.Create would successfully create the campaign (as viewed through the web UI, and a "success" message through the API), but return a Code 0 for the new campaign's ID?
Passing 0 into Campaign.Send returns an Invalid CampaignID error.
Many thanks to David at CM Support for pointing out my error. The return code passed back to you by Campaign.Create holds a 0 for Success or another number indicating an error. The campaign ID can be found in the ReturnObject property.