Hello there, I have the CSSU-Thumb repository enabled, and when I go to Xterminal, and execute:
to install CSSU, it throws a bunch of repository errors and dependencies like, depends on bla bla bla version 3 but 2 is to be installed, a lot of them.
My N900 is clean, right after a reflash and PR1.3.1 update. Help?

Hello,

Simply go to: http://wiki.maemo.org/Community_SSU

and click on either stable or testing link.

Then the full process of repo configuratino and everything will start.

EDIT, did not see you want the Thumb one.
so once the above is done, go to:

http://talk.maemo.org/showthread.php?t=84829

and click on the thumb install link

http://wiki.maemo.org/Community_SSU/Installation_FAQ

Read the first Q and A from that link.

Also enable, Nokia System Software Updates and maemo extras repositories as well as the CSSU repositories.

That exactly what is causing errors, but my N900 is clean! Nothing installed!
Nokia repositories I think aren't updating because of signature key thingy problem, what should I do?

http://talk.maemo.org/showthread.php?t=84829&page=104
There might be some explanation there about the signature key.