I am using iCal version 5 and above and I have two google cals synchronizing with my iCal - Cal A and Cal B.
When I create an event it goes to my default Cal A (which gets synced to Google Cal A). If I change this event in iCal to make it be an event in Cal B instead of Cal A, the event either disappears or after a quick iCal update it goes back to being an event in Cal A.
Since my default cal is Cal A, I have no way to enter new events in Cal B.
Doing all this from Google creates no problem, it's only when I do this from the iCal on my Mac.