Right well you need to see if you can find drivers for the LAN/network adapter that will work better. You may be able to update the ones you have got or if not try some slightly older ones.
Make sure that is the only thing that is giving you problems though. Just because it is the first you've found doesn't mean everything else is fine.
Don't worry about the flashing screen for now, deal with one problem at a time or you will just get bogged down.