It sounds a little odd indead.
I think the problem is probably related to the ESD(Enlighted Sound Daemon), It is the daemon Gnome uses. Kde uses aRts.
I donīt use gnome, but try this:
Play around with the ESD settings, specially disable it, and see what happens.
I once had a sound problem that got solved when i disabled aRts.
Try that and see if it works,