The incorrect placement of the running head is a bug in dateiliste.sty. Loading the babel package causes dateiliste to run the command \dateiliste@babel which in turn runs \addto on \extralanguage for a short list of languages including English. Unfortunately, a number of line endings in that code are not commented out, resulting in some extra spaces, and these work their way in to the page marks. This is apparent even with standard book, but below is a minimal example in your set-up. Note that \listfiles is added to the preamble to prevent dateiliste going into its infinite loop.
\documentclass[english]{scrbook}
\usepackage[a6paper]{geometry}
\usepackage{babel}
\usepackage{dateiliste}
\usepackage{blindtext}
\listfiles
\begin{document}
\mainmatter
\chapter{Heading}
\blindtext[2]
\end{document}

To correct this, copy dateiliste.sty to a new file and correct the definition of \dateiliste@babel so that lines end with % percent signs after closing brackets }. Below is the English part of that definition.
\newcommand*{\dateiliste@babel}{
\addto{\extrasenglish}{%
\renewcommand*\fileListPreamble{%
Here is the list of all files used during the run of \LaTeX{}
which produced this document.\footnote{More precisely, it is
the list of files used one \LaTeX-run before the one which
produced this document, but after some runs the list
should stabilize.}
}%
\renewcommand*\fileListName{List of Files}%
\renewcommand*\fileNameName{file name}%
\renewcommand*\pageName{page}%
\renewcommand*\dateName{release date}%
\renewcommand*\verName{ver.}%
\renewcommand*\descriptionName{description}%
}%
Using the new style file gives the following output with the heading correctly flush left.

Alternatively, you can move the babel package after the dateiliste package, delete the offending hook and, if you need them, make the specific definitions:
\documentclass[english]{scrbook}
\usepackage[a6paper]{geometry}
\usepackage{dateiliste}
\usepackage{babel}
\makeatletter
\let\dateiliste@babel\relax % Clear the hook
\makeatother
%% Make the English definitions
\renewcommand*\fileListPreamble{%
Here is the list of all files used during the run of \LaTeX{}
which produced this document.\footnote{More precisely, it is
the list of files used one \LaTeX-run before the one which
produced this document, but after some runs the list
should stabilize.}
}%
\renewcommand*\fileListName{List of Files}%
\renewcommand*\fileNameName{file name}%
\renewcommand*\pageName{page}%
\renewcommand*\dateName{release date}%
\renewcommand*\verName{ver.}%
\renewcommand*\descriptionName{description}%
%% End of English definitions
\usepackage{blindtext}
\listfiles
\begin{document}
\mainmatter
\chapter{Heading}
\blindtext[2]
\end{document}
dateilist– egreg Oct 6 '12 at 16:58\dateiliste@mainfileadds the main file (i.e. the file you are compiling) to the list of files. Somehow, something is putting that into a loop. Try\usepackage[noaddmain]{dateiliste}– Scott H. Oct 6 '12 at 21:14