Did you install english version Java or french? I'm not sure that would make any difference since the differences are probably only in the install instructions.
After changing Language in LW, you must restart LW. Close the LW program & re-open. Make sure you are opening the LW program & not continually opening the installer instead by mistake.
ie: Start menu -> All Programs -> LimeWire -> LW.
Oh ... you 'might' need to have french fonts, etc. installed on your computer system also.