I have an account as well. I haven't had a problem after downloading multiple times directly to the tablet. All I've ever done is authenticate myself with my user/password. Microb will then prompt you to select if/how you want your password saved. If you select the option for MicroB to save your credentials, the next megaupload link you hit, will automatically start the download, just as it does on your desktop/laptop.

hope that helps.