Sudden strange (color) errors in imaxima



For some reason, my imaxima (maxima 5.30.0, compiled with SBCL) is suddenly
behaving badly in my emacs 23.3.  Here's what happens:

(%i1) 2+2;

LaTeX error in: \mbox{\tt\red(\mathrm{\%o1}) \black}4
(%i2)

I've had this problem before, but I can't remember how I solved it.  And
yes, breqn.sty, color.sty are all installed and accessible (according to
kpsewhich).  It makes no difference if I set imaxima to use "maxima" or
"rmaxima" as the executable.

Any ideas or advice?  Thanks!

-Alasdair