command "man" doesn't work, please help!

[Lina Wang <Lina wang umist ac uk>]

Dear List,

i am running RH 7.0 with the upgraded kernel 2.4.2. i came across a
problem with "man" today.
when i run "man traceroute" (or any command), it doesn't display anything
except the "END" at the bottom of the screen. then when i exit from it, it
says:
/usr/bin/groff: can't find `DESC' file
/usr/bin/groff:fatal error: invalid device `latin1'

i did "rpm -qa|grep groff", and i got:
groff-gxditview-1.16-7
groff-1.16-7
groff-perl-1.16-7

pachage groff is properly installed. could anybody give any
suggestions. your help is highly appreciated.

Lina