Probably already done this but some most audio driver
when loaded have the mixer settings set to zero volume
or mute.
Kill any sound servers that are running like esd or
jack. i think RH8 has the esd sound server (not sure).
Look at the info files on the driver loaded and check
that it´s actually the right one. (i have had RH auto
detect wrong, several times)

Check all system logs for any other hints tom what can
be wrong.