Can't assign Launcher-icons

[Ewald Jenisch]

Hi,

I'm having trouble assigning icons to applications in the "Launcher
Properties" under Gnome:

When opening the Properties window ("Launcher Properties") and
clicking on "Icon" near the bottom of the window I can't assign
e.g. .png, .gif, .xpm or whatever graphic-file as an icon: All entries
(filenames) are grayed out so I can't click on them.

This happens for any graphic-files not contained in the standard
icon-directory, i.e. /usr/X11R6/share/gnome/pixmaps.

Does anybody know what to do in order to assign icons (i.e. .png,
.gif,...) to programs started via a launcher?

Thanks much in advance for your help,
-ewald