Sync w. Google calendar: Events being deleted prior to 4 weeks ago

I'm using standard Google Calendar to sync with both iCal on my Mac (v. 4.04, MacOS 10.6.7, syncing via CalDav) and with my iPhone (iOS 4.4.3, also set up as a CalDav account).

I noticed some time ago that almost all events that were in my calendar more than 4 weeks ago are being deleted. A handful of events are still in the calendar, which seem to mostly be instances of recurring events. The deletion is a rolling cutoff -- as today's date moves forward, the next date before the 4-week window is erased. So at any given time, I only have the last 4 weeks' events and future events, but nothing from before 4 weeks from the current day's date. My phone is set to sync all events, not just the past 30/60 days.

Oddly, my wife's computer and phone do not have this problem -- all her events are still there. Her configuration is an identical setup for iCal and Google Calendar but her iPhone is a 2G syncing with Google Calendar via IMAP.

My wife's calendars are in a separate account and we are each subscribed to the others' calendars. This is set up as delegates in iCal and just using our own calendars account on the iPhones, which shows all the calendars (including the others').

Anyone have an idea why this would be happening? Or at least how to narrow down the problem to either my iCal or iPhone?!?