Some problem with sound in Gnome

[Nightshade <nightshade tiscali it>]

Hi, sorry if I send this mail to the wrong address but it's the one I found...
That's my problem. When I access to gnome as root, sound server works fine! 
But when I try access as normal user, I don't listen anythig, or better, I 
can hear the mp3 "preview" by browser going on with the mouse pointer, I can 
hear other music but, i.e. the startup sound not! Any solution?
I hope to have been clear. :-) 
Tnx in advance, Jonny