Someone changed the behaviour when activating Layout->Document-Paper->Custom Sizes.
All input fields show the value 0. this is wrong! geometry has default values for the lengths, so that these inputfields have to leave empty, to get the predefined values. Now we have a latex output like \geometry{verbose,a4paper,tmargin=0cm,bmargin=0cm,lmargin=0cm,rmargin=0cm,headheight=0cm,headsep=0cm,footskip=0cm} and it should be \geometry{verbose,a4paper} when I do not input any length. Herbert -- http://www.lyx.org/help/