OK, so it is the calendar. Somewhere in Outlook Calendar you have and error in the data. I don't know how to tell you which is the 298 entry, I have read that they are consecutive, i.e., the order you entered them.
Is this the first time you have synced with Outlook? If you have in the past, then the error is likely coming from a newer record.
Read this thread also... lots of people have found attachments to a calendar entry in Outlook, that's the bug, removed the attachment, all works well. MS Outlook synchronization error
Also, you are using the latest 4.2 Desktop Manager, but it is it Service Pack 1? I read that updating DM to that version has cleared the problem also, although I am thinking you are ok there.