Description of problem:

  Anaconda displays useless error message dialog when it cannot read the
installation medium (DVD):

  +----[Error]----+
  | OK            |
  |          [OK] |
  +---------------+

Version-Release number of selected component (if applicable):

  anaconda from the F9-Beta DVD image

How reproducible:

  every time

Steps to Reproduce:
1. Insert F9 Beta DVD and boot from it in graphical mode.
2. Check/Verify the DVD when asked about it (still in text mode).
3. Watch DVD being ejected while anaconda asks you whether you want to [test] 
another medium or [continue] with the installation.
4. choose [continue] and re-insert the DVD tray
5. Watch anaconda try to read from the DVD while the DVD drive is still
detecting the drive. Anaconda's read will fail and anaconda will display the
completely useless error message.
  
Actual results:

  Nonsensical error dialog as depicted above.

Expected results:

  1. Anaconda should retry a few times.
  2. If reads still fail after 5 to 10 seconds, an error message telling about
the problem and proposing useful courses of action. 

Additional info: