I installed Fedora Core 14 with the intention of my home partition
common to Ubuntu and Fedora. Now I can only boot into Fedora.

Both systems halt and give the same error of 'Could not update
ICEauthority file /home/pat/.ICEauthority'

Fedora lets me continue after clicking the box, but Ubuntu does not.

Please can someone help in fixing this and also explaining what this
file is/does. I have found it and as far as I could see it has nothing
inside it.