The scanbuttond workaround worked for me too (LiDE25 scanner).
I installed the package scanbuttond with synaptic. I entered the command
scanbuttond
as a normal user from a Terminal window.
Magically both xsane and xscanimage started working, both as a standalone and with gimp.
Kooka worked too.
If I killed scanbuttond then xsane, xscanimage and kooka became broken again.
The scanbuttond workaround worked for me too (LiDE25 scanner).
I installed the package scanbuttond with synaptic.
I entered the command
scanbuttond
as a normal user from a Terminal window.
Magically both xsane and xscanimage started working,
both as a standalone and with gimp.
Kooka worked too.
If I killed scanbuttond then xsane, xscanimage and kooka became broken again.