Hi, I've hit an annoying problem in LaTeX. I've got a tex file of about 1000 lines. I've already got a few figures, but when I try to add another figure, It barfs with:

! Undefined control sequence.
<argument> ... \sf@size \z@ \selectfont \@currbox

l.937 \begin{figure}[t]

If I move the figure to other parts of the file, I can get similar errors on different lines:

! Undefined control sequence.
<argument> ... \sf@size \z@ \selectfont \@currbox

l.657 \paragraph
                {A Centering Algorithm}

If I comment out the figure, all is ok.

%\begin{figure}[t]
% \caption{Example decision tree, from Reiter and Dale [2000]}
% \label{fig:relation-decision-tree}
% \centering
% \includegraphics[keepaspectratio=true]{./relation-decision-tree.eps}
%\end{figure}

If I keep just the begin and end like:

\begin{figure}%[t]
% \caption{Example decision tree, from Reiter and Dale [2000]}
% \label{fig:relation-decision-tree}
% \centering
% \includegraphics[keepaspectratio=true]{./relation-decision-tree.eps}
\end{figure}

I get:

! Undefined control sequence.
<argument> ... \sf@size \z@ \selectfont \@currbox

l.942 \end
          {figure}

At first, I thought maybe LaTeX has hit some limit, and I tried playing with the ulimits, but that didn't help. Any ideas?

i've got other figures with graphics already. my preamble looks like:

\documentclass[acmcsur,acmnow]{acmtrans2n}
\usepackage{array}
\usepackage{lastpage}
\usepackage{pict2e}
\usepackage{amsmath}
\usepackage{varioref}
\usepackage{epsfig}
\usepackage{graphics}
\usepackage{qtree}
\usepackage{rotating}
\usepackage{tree-dvips}
\usepackage{mdwlist}
\makecompactlist{quote*}{quote}
\usepackage{verbatim}
\usepackage{ulem}