From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; es-ES; rv:1.4.1)
Gecko/20031114

Description of problem:
When trying to unmount a CD from a CD-RW or from a USB flash drive
after accessing an MP3 or multimedia file Nautilus returns the next
message:

Nautilus can't unmount the selected volume

using 

killall fam

as root allows to unmount the volume

Version-Release number of selected component (if applicable):
nautilus-2.4.0-7

How reproducible:
Always

Steps to Reproduce:
1.Mount a CD or USB flash drive
2.open a MP3 or another multimedia file
3.close the file
4.close Nautilus
5.unmount
    

Actual Results:  Nautilus returns:

Nautilus can't unmount media



Expected Results:  The media should be unmounted.

Additional info:

Seems related to fam. Killing fam allows to unmount the volume.