MSI 3.0 and Winxp SP2

My windows installer service is not starting when it is needed if set to manual. For some reason, whenever i try to install/repair/remove a program, i get "can not access windows installer service." Shouldnt the thing start automaticly if not disabled? I am also getting an error message in msword 2003 sp1 which says "the document could not be registered ..." which i think is related to the windows installer not starting. Anyone experienced this or know how to help? Im thinking i need to reinstall msi ... iv already tried most of the fixes iv found on the web with no luck. (reregistering msiexec, etc) The problem is i cant find an MSI redistributible for v3! This seems to have happened shortly after (or right after?) i installed sp2 (and therefore msi 3.0) on my new winxp machine.

PS. I have found that when the serviec is set to automatic, its starts with the system ... then shuts down (stops) whenever i try to run an msi file. If i then go the the service mmc and start the MSI service, the install works fine.