User locked out?

I just installed 10.04/32bit for a neighbour (and young son) on her
fairly old but reasonable spec Vaio laptop.

The actual installation went ok (including shuffling / resizing the XP
/ NTFS partitions to make space), I installed restricted-extras and
then it updated itself.

After that any update or use of Synaptic created errors and that
seemed to be down to some sources being deactivated?

I re-enabled them and things seemed to start going again (I was able
to install Pan via Synaptic etc).

Then I removed Evolution (via Synaptic) and now when I try to log in
(as her) it just throws me back to the login screen?

If I start in Recovery Mode I can log in as that user and authenticate
ok but if I enter 'startx' it comes back with:

X: user not authorised to run the X server, aborting.

.. so I'm guessing removing Evolution also removed something that was
required? ;-(

Repair broken packages didn't help either (FWIW).

So, is there a quick way to fix whatever's broken please (outside a
reinstall) and why would removing Evolution or any of it's associated
bit break Ubuntu so?

Cheers, T i m