While synchronizing my PocketPC (Windows Mobile 6.5) with Google and Outlook, I started getting an error "the following appointment failed to synchronize from the device". The issue at hand was a birthday that was probably deleted but left a ghost appointment somewhere.
Fortunately, after reading a while and searching for the right solution I came across the thread above that worked.
Using SKTools to view Recurring Appointments, in the PIM section, instead of Outlook, helped to find the one that was causing the problem. Issue was deleted and the sync continued without problems.