When you're adding something, there should be a field named "Calendar". Make sure that it's saving to the correct one. What I mean is, on my phone, it defaults to my Google calendar after 2.2. Before 2.2, I had your same problem because I wanted it saved to Google Calendar, but it was saving to the phone's calendar.
If you select that field, it should give you the option to choose if you want it saved to the Google Calendar or your phone's calendar, which I was surprised to learn are two different things. Hope this helps.