tedcousens:
In addition to any "calendars" (IE, Google or Exchange) that you're syncing to over the network, there's one built into the phone. That's the "My Calendar" one. Unfortunately, it's the default calendar for new events and I've discovered no way to change that behavior.
japclev:
I'm not sure how Google's sync works with multiple calendars on a single account - do you have one designated your "default"? Theoretically that would be the one that would sync with your phone; whether or not the other ones will is beyond the scope of my experiences.