I doubt that this is your problem, but it is something to be aware of. Service pack 1 for office 2007 will cause some things not work correctly with previous versions of office and infopath. I had the problem with code working, I uninstalled and reinstalled office and infopath without service pack one, redeployed the forms, and 2003 users had no problems as well as people with office 2007 sp1.