It could be because I set something up incorrectly, but people have been seeing unusably narrow text entry boxes (TEXTAREA) in Movable Type 2.51 with Mozilla (1.0 and 1.2.1), Opera 7 and IE 6.0. So I ran:
mkdir new && for i in *.tmpl; do cat $i | sed -e \
's/<tmpl_if name="AGENT_MOZILLA"> cols=\"\"<\/TMPL_IF>/\
cols=\"80\"/g' > new/$i; done && cp new/* ./
in the tmpl directory and it all seems to be usable now. This is probably not the Right Way(tm) but it makes the entry boxes usable.