I had the same trouble some months ago.
I was desperated with my dumb lady...
Until I test a little trik. Why not re-start the system?
I got out the DVD disk map from the box and tested it was not in the display (No DVD message).
After that I insert the DVD newly in the box and reinit (a simple re-start) the system.
The dumb lady was there!!
Try to do all of that... and good luck!
With a DVD - DL read-write unit, Alcohol 120% last version and a DVD+R DL 8.5GB recordable... no problem!
I just backuped my navigation DVD and works fine. The original is a black one, made by AISIN AW and NaviTech and was in a RX-300.
Good luck.