Synchronize with multiple calendars
I recall having this issue with some calendar not showing up. If I remember correctly it had to do with having some calendar disabled/hidden in google calendar at the time of the first sync; the calendar app would then not bother looking for other calendars.

Try going in Settings > Accounts and Sync > Auto-sync and uncheck it.

Go to google calendar on the web, make sure all your calendar are visible.

Then in Settings > Applications > Manage Applications > All > Calendar Storage > Clear Data

Back to Settings > Accounts and Sync > Auto-sync , check it.

When you next open your calendar, it should be empty, but you should be able to select all your calendars.