Author list goes outside margins in the ACM SIGCHI template

For some reason having 4 authors in this ACM SIGCHI template renders it outside the right margin. See more details and image here.

I suspect the problem is with .cls but I have no idea where to start. Here are the relevant lines in the .tex source:

\numberofauthors{4}
\author{
\alignauthor Aaaaa Aaaaaaa\\
\email{author@a.com}
\alignauthor Bbbbbbb Bbbbbb\\
\email{author@b.com}
\alignauthor Cccccc Cccccc\\
\email{author@c.com}
\alignauthor Ddddddd Dddddddd\\
\email{author@d.com}
}

\maketitle

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The link to the cls file in your link is broken. –  Willie Wong Dec 13 '10 at 1:44
fixed. sorry about that. –  amh Dec 13 '10 at 5:33

If the template is the same as what you can get from http://www.acm.org/sigs/publications/proceedings-templates then have a look at question 18 in their FAQ (scroll, don't click).

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Thanks! This is exactly what I wanted. I should have Googled more. –  amh Dec 14 '10 at 5:55

The class seems explicitly set up for maximum 3 authors. For more than 3 it seems to want you to do something like:

\numberofauthors{5}
\author{
\alignauthor Author 1\\
\email{author@a.com}
\alignauthor Author 2\\