I had the same problem to play audio cd's with XMMS under my normal user account, even though I could play them when logged in as root. To solve the problem, make yourself a member of the cd-rom group. I don't know how you would do that with Red Hat - I used the User Manager utility in KDE to do it.
Added on 01-16-2004: I reinstalled Debian (it's a long story...) and once again experienced the silent audio cd problem with my user account, even after adding myself to the audio and cdrom groups. Turns out that I also had to belong to the disk group... Now it works