To my surprise (nath does a lot of low level catcode changes), swapping the load order of nath and biblatex works.

\documentclass[
paper=A4,
pagesize,
fontsize=10pt,
draft=false
]{scrartcl}
\usepackage[style=numeric-comp,
bibstyle=numeric,
sorting=none,
url=false]{biblatex}
\usepackage{nath}
\addbibresource{ref.bib}
\begin{document}
\begin{equation}
(\sum_{i=1}^n x_i^p)^{\displayed{\frac 1p}}
\end{equation}
\cite{test}
\printbibliography
\end{document}
with ref.bib containing
@Article{test,
author = {Author, A. N.},
title = {Title},
journal = {Journal},
year = 2010
}
File versions
The following versions of files were used in this example:
*File List*
scrartcl.cls 2012/07/29 v3.11b KOMA-Script document class (article)
scrkbase.sty 2012/07/29 v3.11b KOMA-Script package (KOMA-Script-dependent ba
sics and keyval usage)
scrbase.sty 2012/07/29 v3.11b KOMA-Script package (KOMA-Script-independent
basics and keyval usage)
keyval.sty 1999/03/16 v1.13 key=value parser (DPC)
scrlfile.sty 2012/06/15 v3.12 KOMA-Script package (loading files)
tocbasic.sty 2012/04/04 v3.10b KOMA-Script package (handling toc-files)
scrsize10pt.clo 2012/07/29 v3.11b KOMA-Script font size class option (10pt)
typearea.sty 2012/07/29 v3.11b KOMA-Script package (type area)
biblatex.sty 2013/01/10 v2.5 programmable bibliographies (PK/JW/AB)
biblatex2.sty 2013/01/10 v2.5 programmable bibliographies (biber) (PK/JW/AB)
etoolbox.sty 2011/01/03 v2.1 e-TeX tools for LaTeX
etex.sty 1998/03/26 v2.0 eTeX basic definition package (PEB)
kvoptions.sty 2011/06/30 v3.11 Key value format for package options (HO)
ltxcmds.sty 2011/11/09 v1.22 LaTeX kernel commands for general use (HO)
kvsetkeys.sty 2012/04/25 v1.16 Key value parser (HO)
infwarerr.sty 2010/04/08 v1.3 Providing info/warning/error messages (HO)
etexcmds.sty 2011/02/16 v1.5 Avoid name clashes with e-TeX commands (HO)
ifluatex.sty 2010/03/01 v1.3 Provides the ifluatex switch (HO)
logreq.sty 2010/08/04 v1.0 xml request logger
logreq.def 2010/08/04 v1.0 logreq spec v1.0
ifthen.sty 2001/05/26 v1.1c Standard LaTeX ifthen package (DPC)
url.sty 2006/04/12 ver 3.3 Verb mode for urls, etc.
blx-dm.def
numeric-comp.dbx
biblatex-dm.cfg
blx-compat.def 2013/01/10 v2.5 biblatex compatibility (PK/JW/AB)
biblatex.def
standard.bbx 2013/01/10 v2.5 biblatex bibliography style (PK/JW/AB)
numeric.bbx 2013/01/10 v2.5 biblatex bibliography style (PK/JW/AB)
numeric-comp.cbx 2013/01/10 v2.5 biblatex citation style (PK/JW/AB)
biblatex.cfg
nath.sty
english.lbx 2013/01/10 v2.5 biblatex localization (PK/JW/AB)
q.bbl
***********
nathanbiblatex? – DaPhil Mar 04 '13 at 08:06nathpackage also looks rather old. Sad that it's development is frozen. It has some features that makes math much more straightforward. On the other hand, biblatex is must... There is no other package which is more compatible with everything else (biblatex is not the only package which causes problems) that has some of the nice featuresnathoffers? – DaPhil Mar 04 '13 at 08:39