I also have had problems like this between Outlook and my Storm. I have lost all data when carrying out a two-way synch in the past when I was not careful enough to check the details of the synch process.
Right now, despite using the 'forever' setting, items in the previous month (January) have disappeared. When running synch, the process wanted to delete all the appointments from Outlook too. I managed to get them back onto the Storm using ReSync.
But I'm very confused as to what is going wrong.
I tried 'pulling the battery