If Dolphin has worked in the past then it may be running currently in a problem state as a process in the background.
So, see if Dolphin is running and then kill any running Dolphin processes and then try starting Dolphin afterwards.
The Dolphin process in KDE 3.5 is named "d3lphin". I don't know what it's called in KDE4. I used the wildcard below because I don't know the name of the Dolphin process in KDE 4.
Try locating any currently running Dolphin process and kill them:
$ ps aux | grep "d*lph*"
$ kill [PID]
Replace [PID] with the process ID returned via your "ps" output. If you find any running Dolphin processes kill them. Then try starting Dolphin again.
If the above fixes the problem consider using htop which is a nicer way to play with top and kill processes. htop is available in package repos.
For information on running ps and kill see their man pages:
$ man ps
$ man kill
--- On Mon, 8/4/08, Karl Vanwynsberghe <firstname.lastname@example.org> wrote:
> From: Karl Vanwynsberghe <email@example.com>
> Subject: Kubuntu KDE4.1 - Dolphin won't start
> To: "Kubuntu Discussions" <firstname.lastname@example.org>
> Date: Monday, August 4, 2008, 3:08 PM
> After trying to start Dolphin, i get an bouncing icon for
> about 30s and then
> nothing anymore.
> What could be the cause for not booting up the program?
> (thx for the help....)
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