Having just installed a new Fedora Core 2 system, I'm reminded of a problem I think I had with Fedora Core 1 too, and LyX 1.3.4:
When trying to spell-check in French, I get the error: "Cannot open /usr/lib/aspell/frenchb" This is fair enough, there's no such file. Copying the existing "french.alias" to "frenchb.alias" solves the problem, but it seems that "frenchb" is not a valid language name as far as aspell is concerned, and LyX should be using the right name. -- http://rrt.sc3d.org/