\mathtt is currently not properly displayed in LyX. This is just an "optical issue" but qualifies as a bug I suppose.
The attached patch fixes that. Ok to apply? Andre' -- Those who desire to give up Freedom in order to gain Security, will not have, nor do they deserve, either one. (T. Jefferson)
Index: math_support.C =================================================================== RCS file: /usr/local/lyx/cvsroot/lyx-devel/src/mathed/math_support.C,v retrieving revision 1.64 diff -u -p -r1.64 math_support.C --- math_support.C 11 Dec 2002 06:45:19 -0000 1.64 +++ math_support.C 21 Jan 2003 11:57:17 -0000 @@ -538,6 +538,7 @@ fontinfo fontinfos[] = { {"mathrm", LyXFont::ROMAN_FAMILY, inh_series, inh_shape, LColor::math}, {"mathsf", LyXFont::SANS_FAMILY, inh_series, inh_shape, LColor::math}, {"mathbb", LyXFont::MSB_FAMILY, inh_series, inh_shape, LColor::math}, + {"mathtt", LyXFont::TYPEWRITER_FAMILY, inh_series, inh_shape, LColor::math}, {"cmex", LyXFont::CMEX_FAMILY, inh_series, inh_shape, LColor::none}, {"cmm", LyXFont::CMM_FAMILY, inh_series, inh_shape, LColor::none}, {"cmr", LyXFont::CMR_FAMILY, inh_series, inh_shape, LColor::none},