newrecommand doesn't work

[monty]

I've tried to change the chapter name like this:
\renewcommand{\chaptername}{Practic}

But in the dvi, or ps, it still shows "Chapter".

I've exported it to latex, but the problem remains.

Also i put \chaptername to verify that it hadn't changed.

any idea about this?. It's very extrange.

Using report template on lyx 1.1.6fix2.

thank you in advance.