I removed ubiquity-slideshow-ubuntu before starting the installer. Now I get an "Unable to load page - file:/.../ubiquity-slideshow/..." page instead of the crash. After Ubiquity finished copying the files, the installation proceeds without problems.
Persists in Ubuntu 12.04 final, too.
I removed ubiquity- slideshow- ubuntu before starting the installer. Now I get an "Unable to load page - file:/. ../ubiquity- slideshow/ ..." page instead of the crash. After Ubiquity finished copying the files, the installation proceeds without problems.
Thanks for the hint!
Possible duplicates: bug #978489, bug #985354, bug #1014071.