I am using FC5 on a Acer P4 3.2 GHz. XMMS behaves very strangely, if I do not open any applications and then start xmms it runs fine. But if some applications like mozilla or citrix applications are running, XMMS gives error while playing and says could not open sound device. If I close those applns and then again restart xmms it plays fine. How do I see which programs are conflicting with this?

sounds like a mixing problem. not very strange for anythign to behave that way. basically by default your card only supports one stream. you either need to configure your hardware (perhaps a speciffic driver) to support harware mixing or use software mixing.
its something i have yet to do myself, just not enough time... since my sound sorta works when i need it its a low priority right now.
anyone wanna contribute on how to confugure software mixing and make all programs use it?

ps i use oss for most apps since my sound chip manufacturer supplies only the oss driver. they dont say if there is hardware mixing support or not. i dunno how to figure that out yet. its C-Media CMI9739 if anyone is curious. would also appreciate if someone tells me how to enable 5.1 on it.