I ran into a problem formatting things with breqn and the braket style file. A minimal example that illustrates the problem is:
\documentclass{article}
\usepackage{braket}
\usepackage{breqn}
\begin{document}
This does not format correctly
\begin{dmath}
\ket n = (C) = A + B
\end{dmath}
However, this does
\begin{dmath}
\ket n = C = A + B
\end{dmath}
\end{document}
The output of which is: 
While in the above example the parentheses are mathematically unnecessary, in the more complicated example I found this in, I need them.
breqn.sty 2009/08/07 v0.98a. Could you check your version by adding\listfilesin your preamble and looking near the end of the.logfile? – Jake Oct 10 '11 at 23:16breqn.sty 2009/08/07 v0.98aand my problem is fixed. – qgp07 Oct 11 '11 at 15:18