iCal shows an event that the Google Calendar doesn't have?
I've seen this same problem when I use ical for Outlook synching.  Drives me crazy.  Today I figured out a solution.  Go to your Google calendar and "Search" for the offending meeting (just use some key word).  In my case, it found the meetings.  I simply expanded the meeting info in the search results and it allowed me to delete the meeting.  Then, give Outlook some time to resynch and it will be gone.