Hmmm. Not sure. My calendar works great. Everything in my desktop calendar syncs flawlessly to my calendar on my phone and I have multiple Google accounts syncing and facebook. So I'm not sure. You could always find another calendar app in the party store
Did all that, but still can't get calendar or contacts to go from phone to computer.
I was having a similar problem and found that when I started a new calendar event that at the top of that screen was an option for Calendar. I had to set this to my Google email address rather than a Samsung Calendar. As soon as I made this change my appointments created from the phone started showing up online. I am not sure if this has to be done each time an event is created or not since I only discovered this a few hours ago.
Apparently when the JB update came down something changed this setting. Hope this helps.