The problem seems to be reproducible (and is maybe normal).
When I add another xxx.layout to /usr/share/lyx/layouts, the next time I
start up LyX, the menus are gone.
No significant debug messages seem to appear. The fix: blow away ~/.lyx
and restart lyx.
The symptoms have occurred a lot lately, because I have been trying out
presentation classes/styles/layouts with LyX.
Among them pdfscreen, advi, and prosper.
They are all very good! But there is a lot to learn! I will offer
templates and examples when I have got all 3 working to my
satisfaction.
After my utterly disparaging comments about seminar, I must admit that
Dekel's advice to use prosper was well founded.
But there are 3 different versions , and 4 lyx layouts -I am trying to
find the best of prosper, prosper2 (3 variants), and xprosper (for advi).
John O'Gorman