Thanks Richard! I try to give some more informations:

	
	- Mounting doesn't work as root or user

	- It's the first time the problem occurs and mounting
	  definitively worked after system boot.

	- Software I ran: KDE3.3-Desktop, some SVCDs and DVDs with
	  mplayer, KsCD (CD-Player), XCDRoast (CD-Burner) and mounting
	  some multisession CD-Rs. But I don't know which process is
	  blocking the device, 
	  "lsof | grep -i /dev/cd" gives no output

	- Leaving KDE, "shutdown now" and returning from single-user-mode
	  did not help.


Sure, rebooting the system would solve the problem within 4 minutes,but
I don't accept that as a solution - not as yet ;-)

I searched the NetBSD-docs for infos dealing with "busy devices", 
without success. 


Regards, Mark