I bought a new imac 3 days ago. The operating system is version 10.6.3. It tells me I need to update the software which requires a 478 mb download. I have tried at different times all 3 days, but the download always fails. I get a message the download had an error and to try again. I have satellite internet service (Hughesnet) which is not very good, but I have downloaded large files many times without problems. Any ideas what I can do to get this update?