Soso, Hallo Ismaninger Prüftechniker...
Also:
1) Remove the pinning from the /etc/apt/preferences
2) remove the reference to "unstabil" from the /etc/apt/sources.list
3) apt-get update
4) apt-get install kdevelop=x.y.z 
   where x.y.z is the version number of
   the "testing" or "stable" package
5) maybe you need to do 4) with Dependencies to but it depends.
Grüße und schönen Tag/Abend
    Michelle Konzack
    Systemadministrator
    Tamay Dogan Network
    Debian GNU/Linux Consultant
-- 
Linux-User #280138 with the Linux Counter, http://counter.li.org/
##################### Debian GNU/Linux Consultant #####################
Michelle Konzack   Apt. 917                  ICQ #328449886
                   50, rue de Soultz         MSN LinuxMichi
0033/6/61925193    67100 Strasbourg/France   IRC #Debian (irc.icq.com)
Attachment:
signature.pgp
Description: Digital signature