Weird upgrading problem

[Krister Ekstrom]

Hey all,
I was trying to upgrade my Feisty to the latest version this morning
when to my surprice i encountered a strange little problem. I noticed
that the upgrading procedure, (made with the command aptitude
dist-upgrade) had stopped so i went to check the screen and there was a
dialog that said: "Configuring X11Common
Incorrect nice value
Please enter an integer between -20 and 19."
Well, here comes the strange part because there was no edit box to fill
in the value in, and typing numbers on the keyboard didn't give any
result, the only keys that worked were spacebar and enter key and they
only produced the same dialog.
Fortunately this is Linux, so there must be a text file that can be
altered in some way. What file has the config settings for X11-common
and if there isn't a text file after all, what if anything can i do in
order for things to install as normal and do you want me to provide any
other info?
Thanks for any help here.
/Krister