"Local calendar cannot sync with Google calendar..." but it can? What? On my totally stock Bell Samsung Galaxy S2 I have my main GMail account synced to it, it is also synced to my iPod using Exchange ActiveSync.

My phone's default calendar has all the events from my Google Calendar that I had been organizing and creating events from my iPod calendar with. However, when I create a new event I get this error. I tried going to the Account and Sync settings, then syncing the calendar, but the wheel stops spinning after a little bit, then just disappears and the problem remains.

I tried creating a test event, then checking Google Calendar on the website from my laptop and the event was there. Even today, I made an event on the phone and it's on the web page. In fact, I just corrected the time of the event from the web page and the change was reflected almost instantly on my phone.

I tried unchecking the account sync and then deleting local calendar data, then rebooting and resyncing. But the problem persists.

What's wrong? Is there anything I can do? (besides factory reset please!) Or should I just check the "Do not show again" box? Or would that cause a problem later on?

As a side note Samsung Kies popped up first saying it couldn't sync, but I couldn't care less about that since I only made a Samsung account for the find my phone feature and the developer stuff.
If you go into the Calendar app and press the Menu button, then select Settings you should see an options at the top for Calendars this should show all of the individual calendars on your device that are being merged together into the Calendar displayed.

The top one is probably My Calendar then below that should be an entry for your GMail calendar, then maybe Facebook, or Contacts' Birthdays, and any other calendars you may have access to. The My Calendar calendar is purely held locally on the phone, it doesn't sync to GMail at all.

If you don't want to use that, then take the tick out to stop showing it as it sounds like you'd rather have everything syncing to the GMail calendar. Next time you create a new appointment in your calendar scroll down the Create screen to where it says Calendar with a right poiting arrow, select that to make sure that it is saving to your GMail calendar. If so, then you can safely tick the "Do not show again" box on your warning, as you don't care about the phone's local calendar you're saving straight to your GMail calendar anyway.