Segfaults in weird places after aptitude update && aptitude upgrade on clean alternate gutsy install

[Brian McKee]

I've done this three times now, so I know it's not me :-)
After an update my system has weird segfaults, X is unusable.

Sorry it's long, but I'm trying not to leave details out since I can't
clearly define the issue.

Start with a 7.10 alternate cd and an Athlon 2500+ nVidia chipset
computer.

Format (ext3 /boot, XFS / partition and swap partiton on LVM) 

Install.   Everything works fine after the initial installation.

Do sudo aptitude update && sudo aptitude upgrade

It requests a reboot when completed.

After the reboot X won't start - /etc/gdm/failsafeXServer segfaults...

aptitude update works
aptitude isntall someRandomPackage might work - but shows segfaults
e.g.
   Need to get blah blah blah  
   Writing extended state information.... Done
   Segmentation fault (core dumped)
   Selecting previously deselected blah blah

I had a hazy guess that it might be because of the restricted modules -
I have an nVidia Geforce 2 card in this machine that under dapper used
the nvidia-legacy drivers.  Gutsy seemed to install the regular nVidia
driver rather than the legacy ones (or at least the name didn't
obviously show it was using a 'legacy' driver) when I did it the first
time, so this time I ignored the restricted drivers pop-up.   Oddly
though, /var/log/dpkg log seems to show linux-restricted-modules as  a
package that was updated.   Maybe I don't understand all the cases that
would be used.  I mean, it's nVidia ethernet etc as well.

It doesn't seem to be related to the LVM or the XFS file system.  I can
use the file system fine.   I can use wget to pull down a web page.

I'd like suggestions on 

1 - how do I better identify the problem so I can file a useful bug
report

2 - how do I fix this so the system is usable

Thanks for reading,

Brian