disc tray ejection trouble

Strictly speaking, the disc tray mechanism works fine as does the rest of the unit, but my DVD Burner's "eject" button seems to be unresponsive.  I can still operate the ejection mechanism by command, and push the tray back in manually to close it, but this is annoying.  It only just started 10min ago for no reason.  Any solutions or suggestions?

Note: this DVD Burner is a top-of-the-line Sony make and runs wonderfully.

Programs that burn disks like to 'lock' your drives and if they exit improperly or are poorly written they can forget to release those locks.