ubi-partman fails with exit code 141 when setting up crypted partitioned installation

The following crash occurred during a manual crypted partitioned installation of raring desktop,

Feb 22 14:11:33 ubiquity: Partman: auto_state = None
Exception caught in process_line:
Traceback (most recent call last):
  File "/usr/lib/ubiquity/ubiquity/filteredcommand.py", line 145, in process_line
    return self.dbfilter.process_line()
  File "/usr/lib/ubiquity/ubiquity/debconffilter.py", line 287, in process_line
    if not input_widgets[0].run(priority, question):
  File "/usr/lib/ubiquity/plugins/ubi-partman.py", line 2999, in run
    None, request['method'])
  File "/usr/lib/ubiquity/plugins/ubi-partman.py", line 1672, in preseed_script
    question, menu_options, want_script, want_arg)
  File "/usr/lib/ubiquity/plugins/ubi-partman.py", line 1667, in must_find_one_script
    (question, want_script, want_arg))
ubi-partman.PartmanOptionError: partman-target/choose_method should have None (crypto) option

This occurrs with i386,amd64 and amd64+mac images (20130222) desktop installations, live session or otherwise.

Steps:
1. Start the installation and go upto the manual partitioning step (Select something else at the 'Installation type' step)
2. Click 'New partition table' and click continue on the pop up
3. Add a partition and select it as 'physical volume for encryption' , enter the security keys and click OK
4. Now select the crypted partition eabove and click 'Change'
5. In the resulting 'Edit partition' window, select 'Use as' to be 'physical volume for encryption' , enter the security keys again and click OK
6. The crash can be observed at this point. THe logs are attached.

Note: Not very sure if steps 3,4 and 5 are legitimate and could be expected from an expert user. But there were no warnings against these actions in the process.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: ubiquity 2.13.12
ProcVersionSignature: Ubuntu 3.8.0-7.15-generic 3.8.0
Uname: Linux 3.8.0-7-generic x86_64
ApportVersion: 2.8-0ubuntu4
Architecture: amd64
CasperVersion: 1.330
Date: Fri Feb 22 14:11:54 2013
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash --
LiveMediaBuild: Ubuntu 13.04 "Raring Ringtail" - Alpha amd64+mac (20130222)
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)