Works fine as root but not as user? It's a permissions problem. Make sure you're a member of the audio group and all should be well. Use groups to find out what groups your user account is a member of:
users disk floppy audio video cdrom
If you don't see audio in the results, use usermod to fix:
james[~]$su -c 'usermod -g users -G additional,groups,here username
-g denotes primary group. For normal users, this should be users. -G denotes additional groups. List each group you want the user to be in, seperated by commas and without spaces. Of course, username is the username of the account you're modifying.