icloud calendars not appearing in outlook 2007 with google app sync

I'm having trouble getting iCloud to sync my iPad/iPhone calendars with Outlook 2007. The Add-In is present and shows that it is turned on, but the calendar's aren't present. I've previously successfully used iCloud to sync with Outlook on a different computer. I am also running Google App Sync to sync with my work Gmail account - not sure if that's interfering.