K3b depends on udisks for drive recognition thus being unable to find any devices if the udisks USE flag is not set. The reasult is k3b complains about it being unable to find any disks and an error realated to dbus and udisks appears on the screen. Reproducible: Always
Sounds reasonable. We left udev optional in kdelibs because there are some cases when it's not needed (like people installing just kdevelop).
The same thing happens with media-sound/kaudiocreator.
kaudiocreator fixed as well.