The solution for me was quite simple. The URL you are publishing to must be present in the Alternate Access Mapping (AAM) list of your SharePoint site. I was trying to publish to the IP rather than the server name, which was not in said list.

The URL you are publishing to must be present in the Alternate Access Mapping (AAM) list of your SharePoint site.

I was attempting this strange behaviour due to some temporary naming issues that i’m having in my lab network. While most SharePoint folk will not come across this error, I figured it might be useful to throw in my two cents as other people may tossing together temporary sites with little regard to the proper configuration of AAMs.

One of the comments on this blog post clued me in. The person mentioned missing host headers, at which point I realized that IIS probably doesn’t send them if you’re not requesting a “valid” SharePoint URL, as SharePoint itself probably adds the MicrosoftSharePointTeamServices header which Infopath uses to determine if the publishing target is valid.