Utopic ubiquity froze while reformatting existing partition

This is the error I kept seeing respawned:

(ubiquity:3784): Gtk-CRITICAL **: gtk_widget_set_allocation: assertion 'gtk_widget_get_visible (widget) || gtk_widget_is_toplevel (widget)' failed

I repeated this test to be sure it wasn't a fluke or an error on my part and it was easily reproduced. Just select a partition with a pre-existing Ubuntu family install (in this case it was a simple pre-existing / with only an assigned swap - no /boot or /home) then keep the existing size, select ext 4, select format, and select / as the mount point.

No formatting even begins because I'm still able to boot the pre-existing OS after aborting the install process. I'll repeat ASAP with an Ubuntu iso to see if this is limited to Ubuntu GNOME or not.

This bug has been reported on the Ubuntu ISO testing tracker.

A list of all reports related to this bug can be found here:
http://iso.qa.ubuntu.com/qatracker/reports/bugs/1372953

This does also effect Ubuntu Utopic 20140923 i386 with an added twist. Until a filesystem is selected the ability to select a mount point doesn't appear at all (see screenshot).

In Ubuntu GNOME the ability to select a mount point appears even if do not use the partition is selected.

BTW I'm testing on bare metal if that matters:

Intel Atom CPU 230 @ 1.60GHz
Intel 82945G/GZ Integrated Graphics Controller (rev 02)
Intel N10/ICH 7 Family High Definition Audio Controller (rev 01)
Realtek RTL8101E/RTL8102E PCI Express Fast Ethernet controller (rev 02)
2GB DDR2 RAM

An additional caveat to this failed formatting seems to be creating overlapping partitions, at least if the target partition is a logical partition. I first thought maybe I had an overlapping partition problem prior to the failed installation which could cause things to fail but I used FixParts since it was an extended partition overlapping a primary partition and then repeated the test with the same results, and creating an overlap again, where the extended partition began before the end of the primary partition just before it.

I may be narrowing this down a little bit. What the screen actually says while frozen is; "Creating ext 4 file system for / in partition #13 of ...............".

Also it seems to effect only logical partitions so far but I need to repeat a few tests to verify that.

If I quit the install and format the existing install/partition using Gparted and then restart the install process it works OK.

It does however happen regardless of whether I start the installation from the boot menu or from the live DE.

It does also effect Ubuntu GNOME Utopic 20140926 but the Beta 1 images work OK.

This is actually a duplicate of bug #1361951 - I just have a bad memory.

Status changed to 'Confirmed' because the bug affects multiple users.