Entourage for Mac question

At my office I just got a new iMac with Lion, though I don't think that my issue has much to do with the new software..

I have used Entourage as my email program for several years and have been trying to successfully transfer my identity from my old computer (a G5 running Tiger) to the new one.

Where I'm having trouble is that, while I've been able to import the identity, there are gaps of emails that aren't transferring over. In my inbox, there's about a month missing, and in my sent files about two months (all during the same period, just a few months ago).

Does entourage not update the identity file with every email sent/received? Or is there something I'm missing?

Incidentally, the emails stored on my web server aren't any of the emails missing in the transfer.

Does anyone have any insight they'd be willing to share?

Thanks so much -

kevin