I'm having a bit of trouble with inserting any CDs into the CD drive. The computer doesn't even bother to try and read the CD, it just ejects it as soon as it's inserted. It also doesn't seem like it goes in all of the way, part of the CD is still sticking out of the drive. We're not entirely sure what has happened, but any ideas for fixing it would be helpful. Is it possible that we simply need to clean the lens?