Newbie: Install problems (pre-depend-error, python)

["Thomas Guettler" <guettli@gmx.de>]

I tried to install debian (potato, from march 13th) 
for the first time and have two
problems:
I already have a small running system, and wanted to 
add several packages at once. Dselect says the
following and refuses to install:
pre-depend Error ...... fix it and run [I]nstall again
But it doesn't tell me which package is making
trouble.

I can't install python-base because dblib1.8 is not
available. (There is a package called dblib1 and
dblib2, but none which is called dblib1.8)

Can anyone help me, or tell me where i can find 
help?

Thomas Guettler <guettli@gmx.de>
http://www.mypage.org/guettli