Help with creation, editing, or playback of sounds, images, or video. Amarok, audacious, mplayer, grip, cdparanoia and anything else that makes a sound or plays a video.
Couple suggestions. First, make sure your user account is a member of the audio group. Second, 'chown root.audio /dev/dsp /dev/mixer'. Do a ls -l on this first to check if they're symlinks. If so, chown the file that the link points to. Next, 'chmod 660 /dev/dsp /dev/mixer' (same rules about symlinks applies). Relogin with your user account (to update your group membership) and try it - should work.
As for the default volume, make sure aumix is installed. Set the volume how you like it use aumix (probably works with KMix as well, but I'm not sure), and then click Save the settings as default. This should create a .aumixrc file in your home directory. Copy this to /etc/aumixrc. Next, 'rc-update add aumix default' should set the volume to these setting each time you boot. For extra insurance, launch the KDE Control Center and check Load volumes on login in Sound -> Mixer.