'11 MBP with "up to date" Lion OS started acting flaky with DVD player, then seemed like it couldn't find a startup disk at all. Ran the Apple Hardware test (short and long) via internet. No problems were found. When trying to reinstall Lion, there is no disk to select. I can't proceed to rdo the re-install. Any suggestions ? Could this be hard drive failure, though nothing is noted on the Hardware Test ?