What is the exact error message you recieve?
I encountered a problem with not being able to publish an InfoPath 2007 form to MOSS 2007 document library as a content type (installed on 64 bit Server 2008) AFTER we migrated our SharePoint installation to a new server. The root problem was the server cache registry key was corrupt so we removed the registry key. Obviously this is a drastic move and should only be attempted if you know what you are doing. We saved the cache first before removing it (just in case).
The file path to the registry key for us is: HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Common\Internet\Server Cache. In the cache locate the site/library/whatever that you're trying to publish to, save it to another location, then delete it from registry, then try publishing the form to SharePoint again to let it recreate a new key.
The error message I received was "URL is invalid" - This may not be the same issue for you but I thought I'd throw it out there.
Good Luck.