Occationally InfoPath displays an error when attempting to open from SharePoint. This is sometimes due to a local copy of the form on a user’s computer that is different then the one on the SharePoint site. To remedy, user’s can clear their infopath cache.
Type in the following command:
(Infopath 2007) C:\Program Files\Microsoft Office\Office12\INFOPATH.EXE /cache clearall
(Infopath 2010) C:\Program Files\Microsoft Office\Office14\INFOPATH.EXE /cache clearall