Hi Christian!
>
> I found out what the problem is. But I do not have a solution to it 
> right now.
>
> #include <ros/ros.h>
> #include <QtGui>
[...]

Do you have any locale environment / language setting that uses "," as 
delimiter? I once ran into a very hard to find similar bug, where 
whenever I was using Qt somewhere, stream parsing in all code wanted my 
system locale (German, "1,5") instead of "1.5", happily changing all 
parameters when parsed.

I don't remember exactly, but there's a way to explicitly set the locale 
back in the code or an environment variable if you're working on a 
non-English system.

Best regards,
Armin

-- 
Armin Hornung                              Albert-Ludwigs-Universität
www.informatik.uni-freiburg.de/~hornunga   Dept. of Computer Science
HornungA@informatik.uni-freiburg.de        Humanoid Robots Lab
Tel.: +49 (0)761-203-8010                  Georges-Köhler-Allee 79
Fax : +49 (0)761-203-8007                  D-79110 Freiburg, Germany