Just validated only the .css document as the site has 500 pages, and the menu are on all....and the css dont have any errors.
I know its not necesarry, but I put the p many years ago, as I needed #menu p,
the menu was complicated and it worked using p, and if I take it away, everything change, not only the style of the word. Anyway dont think that the p is the reason for not being able to view the menu.
I also did a full test on the homepage,
and I had 10 errors and 1 warning, however all the errors is due to a marquee I have since many year, and the other error are due to a chatprogram I installed.
Dont think these thing can make the menu not to work?
However will do a test page eliminating these things to see if she still cant see the menu.