Some errors arise when using the sig-alternate LaTeX class with other LaTeX packages. Here are some of the issues, and their solutions.

amsthm.sty has a problem with proof

Error: 

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LaTeX Error: Command \proof already defined.

Solution: Insert this before using the amsthm package. 

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\let\proof\relax
\let\endproof\relax

algorithm2e.sty: Too many }}}

Error: 
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! Too many }'s.  l.1616     }
Solution: Insert this before using the algorithm2e package. 
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\makeatletter
\newif\if@restonecol
\makeatother
\let\algorithm\relax
\let\endalgorithm\relax