The following problem has appeared a few days ago. I believe I have not changed any settings.
Whenever I open up Calendar under OS 10.8.2 on my MacBook Air it shows just one of the calendars I sync with Google. This one has a tick mark in the calendars list shown under the menu "Window":
When I click on "Window > Calendars" (or "Cmd-0"), all calendars appear:
But when I shut down and open Calendar, only the one calendar shows up again.
I don't know where I can set this to always display all calendars, as it was until a few days ago. None of the calendars are ticked under "Preferences > Account > Delegation", and ticking them changes nothing:
I'm on a German system, so menu items are maybe named differently in English than I translated them. I added some images to make my meaning more clear.