(??? The form submitted without me clicking. Strange.) Anyway, according to lyx.org: "There is a very nasty bug in LyX 1.2.2 configure script: if you configure as root and an error occurs during the configure step (e.g. xforms not found), the the script will delete the /dev/null device. This undoubtly leads to very bad effect, since /dev/null is a very basic device in any unix system." There is an ebuild for LyX 1.2.3 -- I suggest either masking 1.2.2 or marking 1.2.3 as stable.
lyx-1.2.3 is now the default, so this issue is resolved. Closing.