ubiquity crashed with KeyError in partman_edit_dialog()

[CeesSluis]

Binary package hint: ubiquity

I want to install Ubuntu jaunty 9.04 Alpha 2 on an existing partition /dev/sda1 but cannot edit the partition.
Same problem with direct installation and live cd installation.
Using a SAMSUNG HD501LJ SATA 500GB drive.

ProblemType: Crash
Architecture: i386
DistroRelease: Ubuntu 9.04
ExecutablePath: /usr/lib/ubiquity/bin/ubiquity
InterpreterPath: /usr/bin/python2.5
Package: ubiquity 1.11.1
ProcAttrCurrent: unconfined
ProcCmdline: /usr/bin/python /usr/lib/ubiquity/bin/ubiquity gtk_ui
ProcEnviron: Error: [Errno 13] Permission denied: '/proc/5562/environ'
PythonArgs: ['/usr/lib/ubiquity/bin/ubiquity', 'gtk_ui']
SourcePackage: ubiquity
Title: ubiquity crashed with KeyError in partman_edit_dialog()
Uname: Linux 2.6.28-4-generic i686
UserGroups: