Conflict between amsthm and some other package

This is the preamble to a book I'm editing:

\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{xspace}
\usepackage{proof}
\usepackage{url}
\usepackage{xy}
\xyoption{all}
\usepackage{amsthm}
\usepackage{stmaryrd}
\usepackage{amsfonts}
\usepackage{amstext}
\usepackage{algorithmic}
\usepackage{algorithm}
\usepackage{graphicx}
\usepackage{epstopdf}
\usepackage{enumerate}
\usepackage{paralist}
\usepackage{mathrsfs}


Trying to compile this document yields the error:

LaTeX Error: Command \proof already defined.


This error only occurred after the inclusion of amsthm in the above list, which I need for one of the chapters. Obviously amsthm is clashing with some other package in the list, but I have no way of finding which one (the other packages are needed for other chapters anyway).

Is there any way of telling LaTeX to ignore the definition of proof from amsthm, thus hopefully resolving the conflict?

Edit: The class I'm using is monog3, which is provided to me by Oxford University Press. I don't know if I can share its contents, but I have checked and it does contain the conflicting definition:

\def\proof{\trivlist \item[\hskip \labelsep{\bf Proof\ }]}


With this in mind, is there a way to get around the clash?

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This works for me. If you're using TeX Live, I suggest you do an update: tlmgr update --all (I just did that myself.) –  Marc van Dongen Feb 8 '12 at 15:29
Welcome to TeX.sx! Please take a look at advice on creating a minimal working example (MWE), as this may well help you isolate the issue you have. –  Joseph Wright Feb 8 '12 at 15:33
Please, show what class you're using. Probably it's defining \proof. –  egreg Feb 8 '12 at 15:35
@MarcvanDongen I've tried this. It didn't help (but thanks for pointing this out anyway, I definitely needed to update). –  Edward Grefenstette Feb 8 '12 at 16:19
@egreg There is indeed a clash at class level. I've edited the post above. –  Edward Grefenstette Feb 8 '12 at 16:19
If the class defines either a macro or an environment called proof, add the instructions \let\proof\relax and \let\endproof\relax before loading amsthm.