I don't use Duokan, but I see many people disappointed that it doesn't work on 3.1.
So I went here:
http://flip.netzbeben.de/2010/11/duo...ish-gui-today/
Downloaded Duokan, extracted the installer/uninstaller and repackaged it with my exploit.
This is untested as I do not use Duokan myself, but I'm guessing this is what you do:
1. Uninstall/disable all jailbreaks
2. Download the full package here:
http://flip.netzbeben.de/2010/11/duo...ish-gui-today/
3. Follow their directions (copy system files, etc) but instead of copying all the installer "bin" from that package, use the correct "bin" from my package. (No jailbreak is required)
http://www.multiupload.com/ZCKYWXWH2S
Again, untested and converted blindly.