This was my problem:
http://www.linuxtv.org/pipermail/vdr/2010-September/023546.html
Long story short, I could not display DVB subtitles.

The solution was:
Apply a patch from IPTV plugin for VDR (iptv-0.4.2/patches/vdr-1.7.15-disable_ca_updates.patch) to VDR.

I'm using yaVDR 0.2 (It's Ubuntu 10.04 minimal + VDR PPA)

First I created a working directory called "src"
mkdir src
cd src/

Then i got the source code for VDR and IPTV plugin:
apt-get source vdr
apt-get source vdr-iptv-plugin

Then I took care for all of the dependencies:
sudo apt-get install build-essential vdr-dev
sudo apt-get build-dep vdr

Before I aplied the patch "vdr-1.7.15-disable_ca_updates.patch" I had to manualy apply a patch for ttxtsubs, that came with VDR source code. Because "vdr-1.7.15/debian/patches/opt-27_ttxtsubs.dpatch" tries to mess with the same code block in pat.c as the patch from IPTV, building will fail, if you apply the IPTV patch first.

So I opened  "vdr-1.7.15/debian/patches/00list" with a text editor and commented the line with opt-27_ttxtsubs.dpatch
vi vdr-1.7.15/debian/patches/00list

Look for a line:
# Patch needed for the ttxtsubs plugin.
opt-27_ttxtsubs

and change it to:
# Patch needed for the ttxtsubs plugin.
#opt-27_ttxtsubs

I then had to ran:
python vdr-1.7.15/debian/patchcheck.py -u

Now that I made sure that /opt-27_ttxtsubs.dpatch won't run at build time, I had to apply it manualy. First you have to be in the ~/src/vdr-1.7.15/ directory. I then applied the ttxtsubs patch:
patch -p1 < debian/patches/opt-27_ttxtsubs.dpatch

Because opt-27_ttxtsubs patch changed the pat.c file, you have to insert one line from "vdr-1.7.15-disable_ca_updates.patch" in to pat.c with a text editor. Find the lines in pat.c:

           Channel->SetTeletextSubtitlePages(TeletextSubtitlePages, NumTPages);
           Channel->SetCaIds(CaDescriptors->CaIds());
        
Then insert one line from the "vdr-1.7.15-disable_ca_updates.patch" :

           Channel->SetTeletextSubtitlePages(TeletextSubtitlePages, NumTPages);
           if (!cSource::IsType(Channel->Source(), 'I'))
           Channel->SetCaIds(CaDescriptors->CaIds());
          
Then I ran:
dpkg-buildpackage

After some time on my Atom CPU, i got a nice vdr_1.7.15-2yavdr1_i386.deb package which I then installed with:
sudo dpkg -i vdr_1.7.15-2yavdr1_i386.deb

Now my DVB subtitles are showing in their glorious color :)

Because I'm fairly lazy, I'm sending this to the mailing list, where I will be able to find it later. This is the firts time I ever used a mailing list, so I'm probably breaking some etiquete, but maybee someone else could find my "solution" usefull.
And by my "solution" I ofcourse mean Rolf Ahrebenger's solution. Thank you again for all your help!

tvich