Is postcard.exe the parent or child process? If you try to delete manually does it work or does it tell you it cannot be deleted? You can try in safemode but for some reason SEP cannot get it. You may have to do some manual removal.
http://www.symantec.com/docs/TECH101661
You can also run the load point analysis from the symhelp tool as well the symantec power eraser
http://www.symantec.com/docs/TECH170735