Unfortunately the update didn't change anything. I made an extensive "log" again about the problems I ran into, but I won't bore you with all the installation weirdness. Basically I started out with an empty iCal, Address Book and factory reset phone and started adding events to see what happened. Here is a short version of my findings so far:
Started out with a totally empty iCal and factory default phone.
Booting up iCal and activating iCal sync in SyncMate.
Choose to sync both ways, all calendars and put events without category in calendar "Ruben", which is the only calendar in iCal at this moment.
Adding a new timed event in iCal.
Seems to work, the event appears on my phone. Changing the event also seems to work, although I still find it rather annoying that SyncMate keeps syncing and syncing while editing the event in iCal. But at least nothing is crashing and everything looks good so far.
Now adding a new all-day event on my phone. This does not trigger SyncMate to sync by itself, so activating it manually.
Got a "Sync Alert" on my Mac, but the event does NOT appear in iCal. :-( Tried again, still nothing.
All day event does not appear in iCal. Trying a timed event on my phone.
This also does NOT appear in iCal. Trying an all-day event in iCal. SyncMate starts syncing by itself again and the event appears on my phone. So the problem is not with timed or all-day events but SyncMate just doesn't sync my phone back to iCal. Double checking my settings in SyncMate.
Settings seem okay, but I'll try to specifically sync my "Ruben" calendar only this time.
Manually syncing again and the all-day event made in iCal now appears twice on my phone. Deleted both (double) events on my phone, syncing again...
The event disappeared from iCal as well. Made a new all-day event on my phone once more.
Sync Alert about one new event, but it does NOT appear in iCal... at least not on the intended day.
Looking if it turned up somewhere else. It's getting weird again.
The event is nowhere to be found, but I notice the timed event I made in iCal on today (April 8, 2008) also appears on April 8, 1948! Another all-day event I made on the phone for April 9, 2008 (which didn't appear in iCal) seemed to have ended up on March 29, 1008! There is CLEARLY something very wrong with the way SyncMate syncs dates between my phone and my Mac. :-(
Maybe tech-people at your side can figure out what's going on here, so I though I'd post my findings up to this point. Meanwhile I'll start again with a totally empty phone and iCal and track EXACTLY what's happening with the dates, hoping to figure it out myself. I'll keep you posted.