After some more hacking around with a custom list SharePoint gave me this error code: 0x81070215
Basically I’d mangled a list definition while an earlier version of the list still existed. The easy solution in my case (dev) was to simply fire up SharePoint Manager 2007 and use the UI to delete the offending list (stsadm –o forcedeletelist –url http://spsite would have probably done the same thing). In a more serious environment, you’d probably need to redeploy the list bits as they were when the list was created.
Your post helped me out a lot.