I have several calendars that I share with family members and I also subscribe to their calendars (we all have full read/write permissions to each other calendars). The the issue seems to be that when someone makes changes to one of the calendars away from the TouchPad (for example through Google website) the calendars get confused. It might be aggravated by repeating events that were disconnected and modified. Sometimes the events get duplicated or changed back. This only happens if TouchPad has the calendars open. I have seen this happen on both my and my husband TouchPads. At this point I can't use the calendar app.
sorry I don't have an answer for your query but I too experience problems adding events to any calendar but the default google calendar for my account. Even though I have full rights to a shared calendar.
