The attached file gives an error Stijn, I'm not sure if you ever found the resolution. Using \loggingall on your source quickly shows there is, as Taco et al. surmised, an infinite loop. The log file ends with this: ... \bm@command ...nd \z@ {\bm@gr@@p \boldmath {{b^c}} } \makebm #1$->\bm {#1} $ \bm@mchoice ... {\hbox {#1$\displaystyle \m@th #2$ }}{\hbox {#1$\textstyle \m... \bm@gr@@p ...fmmode \bm@mchoice #1{#2}{#2}{#2}{#2} \else \bfseries #1#2\fi \bm@command ...30049 ^{\bm@gr@@p \boldmath {{b^c}} } \makebm #1$->\bm {#1} $ \makelabel ...h {\makebm }\normalfont \bfseries #1 :} \sbox #1#2->\setbox #1\hbox {\color@setgroup #2 \color@endgroup } \@item ...i \fi \sbox \@tempboxa {\makelabel {#1}} \global \setbox \@labels \... l.11 \item[$a^{b^c}$] $a^{b^c}$ You can see the loop, \makebm ends up calling itself. Evidently \makebm cannot be used in \everymath. Even a complete re-archiTeXture will not help :). Good luck, Karl