Outlook 2007 doesn't sync with icloud after updating to NIC 2012

I am using Outlook 2007 on my PC and have been synchronizing it with my iPhone via iCloud without problems until I installed NIS 2012. Now, new entries made in my outlook calender will transfer to iCloud and iPhone, BUT if I make a new entry on my iPhone, it will only transfer to the iCloud, but not to outlook. Any ideas why this is happening? Could it be that Norton is blocking it somehow?