As other questions have suggested, I just installed all texlive packages into my system and it did not solve the problem of Lyx not finding classes.
Has this been fixed since 12.04 or is it still a problem?
Could this be related to the texlive directory being outside the original texmf system?
I solved this using this post.
https://tex.stackexchange.com/questions/197730/lyx-not-accessing-styles-classes-and-bibliographies
Please try backing up your LyX home folder (find its location in Help > About) and then removing it. Do that without LyX running. Then start LyX.
You need to delete your home .lyx directory from outside of lyx and then rerun lyx. It reconfigures and then the class .cls files are found. Must be a caching issue.
