Hi, I have downloaded ftp://ftp.lyx.org/pub/lyx/stable/patch-1.2.1.gz and applied it to lyx-1.2.0 as described in the file. I think you should remove the following files from the patch:
development/lyx.spec lib/doc/LaTeXConfig.lyx sourcedoc/Doxyfile src/version.C since they are generated from the *.in versions (and they are removed by "make distclean"). Thanks for LyX, Marcello
