You would need to have a version of Real Player compiled for ARM / Debian which may be why you are having problems. The Media Players handle some streams of audio but are extremely limited on bandwidth.

I haven't found it but there was a statement somewhere that only certain forms of Real Player files will play on the N800. I forget which kind though.

ORB or something may be your best bet - taking the file format and changing it to something that is better handled by the N800.