My Issue maybe slightly different, but with the same symptoms. First, here is my setup.
I have my Macbook Pro with Entourage and iCal synced inside of Entourage.
My Entourage is setup to use Exchange Server 2007.
I have a WindowsXP machine with Outlook 2007 setup for Exchange 2007.
I also use .Mac sync with my Macbook Pro and my Mac Pro at home.
My Blackberry is synced with BES to the Exchange 2007.
So, If I create a single timed appointment anywhere in the system, i.e. iCal, Outlook 2007, Entourage, it shows up properly everywhere. Proper time zone (I am EST as is the server) and everything. If I create an All day event in Entourage or Outlook, it is created in the EST time zone, and it syncs everywhere. If I create an all day event in iCal, it gets synced to Entourage in the Casablanca, Monrovia time zone, but it looks like it only spans a single day in Entourage, and on my Outlook/Exchange/Blackberry it spans 2 days. If I go into Entourage, I can change it to be EST time zone, and that seems to fix everywhere. If I go into Outlook, it's an all day event in EST that spans from 8 to 8, so it's not easy to fix it in Outlook, short of deleting and starting over.
I prefer to use iCal, as I manage my personal and my professional calendar, and I like to keep them separate, it's a little bit of a run around, but if I only use Entourage and Outlook to setup my work calendar, then it should sync down to iCal just fine, and also be on my Mac Pro at home.
I don't think anything is going to happen on Microsoft's end to address this issue, as it appears to be entirely Entourage. The sync function is setup within Entourage. I'm just going to have to hope that they have better sync support and better Exchange support when Office for Mac 2008 comes out.
Justin