iCal Doesn\'t sync

[c-t-m]

I have a small home based office with seven macs. We use iCal to sync calendars between them. There are a total of about 14 calendars to sync in total. A few months ago, soon after upgrading to Tiger, ago we started having problems with the syncing. Changes don't sync on some calendars, some changes to on other calendars. We keep getting "must reset data" alerts with no explanation. Syncs take a LONG time, even when just limted to calendars and not address book as well. Are the data files themselves corrupt and we need to rebuild? The Apple helpline just said to delete the problematic calendars, though we can't identify the problematic calendars since the issues keep changing. Then Apple said to delete all calendars and re-enter the information. As we have years worth of info, that makes no practical sense. The total calendar size is about 7.2 MB for all 14 calendars.