Unable to install when a partition is corrupted on disk

Binary package hint: ubiquity

I usually test Ubuntu on a partition on an external HDD.
Today I wanted to reinstall natty on it (for various reasons) but it did not work because of a corrupted partition.

Here is what I did (obviously, it used to work):
- Boot on the latest daily-live (via live-usb)
- Plug the external hard drive (with a corrupted partition, ie marked as "unknown" in gparted)
- Launch Ubiquity -> it hangs when clicking "forward" on the first page (the one with "for best results, please ensure...")

Then, when I quit ubiquity and restart it after unplugging the external hard drive, I can continue the installation process (so the problem really comes from the detection of the external HDD).

When I formated the corrupted partition, it worked.
So, it seems that Ubiquity's disk scanning hangs when it encounters a corrupted partition

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: ubiquity 2.5.21
ProcVersionSignature: Ubuntu 2.6.38-5.32-generic 2.6.38-rc6
Uname: Linux 2.6.38-5-generic i686
Architecture: i386
Date: Tue Mar 1 18:47:34 2011
LiveMediaBuild: Ubuntu 11.04 "Natty Narwhal" - Alpha i386 (20110301.1)
ProcEnviron:
 LANGUAGE=en_US:en
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)