Hi

I've freshly installed Ubuntu 10.4 on a new computer. I'm trying to install on it application I need (my old computer is broken and I have to send it to the service). I've managed to install texlive and than I can't install anything else. All software I want to have is what I have succesfuly installed on my old computer (with the same version of Ubuntu), so I don't understand, why terminal says (sorry, the terminal talks half English, half Polish, but I hope it's enough):

maria@marysia-ubuntu:~$ sudo aptitude install emacs
Czytanie list pakietów... Gotowe
Budowanie drzewa zaleznosci      
Odczyt informacji o stanie... Gotowe
Reading extended state information     
Initializing package states... Gotowe
The following NEW packages will be installed:
  emacs emacs23{a} emacs23-bin-common{a} emacs23-common{a}
  emacsen-common{a}
0 packages upgraded, 5 newly installed, 0 to remove and 0 not upgraded.
Need to get 23,9MB of archives. After unpacking 73,8MB will be used.
Do you want to continue? [Y/n/?] Y
WARNING: untrusted versions of the following packages will be installed!

Untrusted packages could compromise your system's security.
You should only proceed with the installation if you are certain that
this is what you want to do.

  emacs emacs23-bin-common emacsen-common emacs23-common emacs23

Do you want to ignore this warning and proceed anyway?
To continue, enter "Yes"; to abort, enter "No"

I was trying to install other editors as well, with the same result. As I decided that I might be sure that I know the package I want to install is secure, finaly I've entered "Yes". The installation ended succesfuly, but editor don't understand any .tex file (.tex files are for sure fine):

this is pdfTeX, Version 3.1415926-1.40.10 (TeX Live 2009/Debian)

restricted \write18 enabled.

entering extended mode

(./Szarfi.tex

! Undefined control sequence.

l.2 \documentclass

{book}

?

What's more, I've realised that in Synaptic Manager there is no package which would be marked as supported by Canonical...

Any tips? Thanks in advance