If you have your laptop set to remove from server on download then the mail won't be available on the ipad unless you already downloaded it. By default the windows mail program removes from server on download so you have to specifically tell it to save a copy on server (so it can be downloaded to other devices).
Similarly, on the Blackberry, if you delete the mail from "mailbox & handheld" it removes from the pop3 server, thus again, making it unavailable on other devices....
Basically, if you've downloaded or deleted your mail before loading it on the ipad then its no longer available. I would venture to bet this is the scenario you're experiencing.
