You probably have a program running in the background that has the sound device open. Either shut down all sound programs, or simply reboot.
Also, to better maintain your Mandriva installation, I have a build environment that will build and install the rpms for the driver, libs and utils. You can get it
here. Just untar it, then (as root), run "make && audio_install".
Let me know if you have problems after this. Also, if you do run into issues, could you post the link from running
this script.