Just to confirm what you are saying:
You can remove the CD just as the 515 starts up but before the OS is
fully loaded? Is that what you meant when you said "I just powered down
the system and then *was* able to open the CD drive". Or did you have
to pry the thing open when it was off? If you can operate the CD with
the button but once the OS is loaded you can't, it would seem to me that
some process is locking the object. On a PC that can be a program that
treats a CD like a hard drive and in that case the program itself has an
"eject" function. What the equivalent would be on a 515, I have no idea.
I don't recall ever seeing this. The pointers about the
case/bezel/faceplate impinging might be a possibility, but if you can
operate the CD when the machine is on but the OS isn't fully loaded, it
sounds like a software issue.