ubiquity crashed with TypeError in function(): Argument 1 does not allow None as a value

Hallo
Testing Ubuntu Desktop amd64 20130325 on an intel based pc.
Loading ubiquity-dm waste a lot of time, all seems slow, but once the session is loaded seems to run ok.
This usb key was already used for one installation on another pc, so probably there are something logged before this install.
At the page Install I tried to click on Erase Ubuntu Raring Ringtail and reinstall, but the window was unresponsive, then apport popup the crash.
Thanks
Fabio

Mar 25 18:38:27 ubuntu ubiquity[4751]: debconffilter_done: ubi-prepare (current: ubi-prepare)
Mar 25 18:38:27 ubuntu kernel: [ 883.039013] compiz[4717]: segfault at f0 ip 00007f5c44bfc377 sp 00007fff4a338a78 error 4 in libcompiz_core.so.0.9.9.0[7f5c44ba3000+b0000
same as bug 1160020

ProblemType: CrashDistroRelease: Ubuntu 13.04
Package: ubiquity 2.13.17 [modified: lib/partman/automatically_partition/question]
ProcVersionSignature: Ubuntu 3.8.0-14.24-generic 3.8.4
Uname: Linux 3.8.0-14-generic x86_64
ApportVersion: 2.9.2-0ubuntu2
Architecture: amd64
CasperVersion: 1.330
Date: Mon Mar 25 18:48:09 2013
ExecutablePath: /usr/lib/ubiquity/bin/ubiquity
InstallCmdLine: noprompt cdrom-detect/try-usb=true persistent file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash -- maybe-ubiquity
InterpreterPath: /usr/bin/python3.3LiveMediaBuild: Ubuntu 13.04 "Raring Ringtail" - Alpha amd64 (20130325)
MarkForUpload: True
ProcCmdline: /usr/bin/python3 /usr/lib/ubiquity/bin/ubiquity gtk_ui
ProcEnviron: Error: [Errno 13] Permission denied: '/proc/15774/environ'
PythonArgs: ['/usr/lib/ubiquity/bin/ubiquity', 'gtk_ui']SourcePackage: ubiquity
Title: ubiquity crashed with TypeError in function(): Argument 1 does not allow None as a value
UpgradeStatus: No upgrade log present (probably fresh install)
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