I'm having the exact same problem. It started Sunday after having no problems with the syncing of these two calendars with iCal for quite awhile. Like you, I also have two Gmail calendars that I sync and manage with iCal, mainly on my MacBookPro. I too see both calendars in Calendar on my iPhone, but one of my Gmail calendars has completely disappeared from iCal on my MacBookPro. Over the last two days this calendar has appeared in my iCal during a couple of the auto-refreshes that are scheduled in setup, but the calendar doesn't stay in iCal for very long after it does show up. I experienced similar problems sporadically with iCal before I upgraded to Mountain Lion. Mountain Lion seemed to stabilize the whole Gmail/iCal syncing situation. For me, however, that joyride appears to be over for the time being.