How to reset dconf settings?

[Volker Wysk]

Hello!

My virt-manager can't add a virtual machine any longer. I suspect that the
user configuration settings (for virt-manager, not libvirt) are broken. I
get this in step 5:

"Failed to find a suitable default network"

And this when trying to install:

    Installation konnte nicht fertiggestellt
    werden: «internal error: No
    ‘bridge’ attribute specified with type='bridge'/>»

("Installation can't be completed: ...")

How can you reset the user settings? I found on the web, that they are
stored in "/org/virt-manager/virt-manager/" and can be accessed by dconf-
editor. But how to reset them? When I uninstall and reinstall virt-manager,
and the many packages which it depends on, the user settings stay the same.

TIA,
Volker