Playing MP3s VIA FS-CIFS SHARE

Because of my acquisition of a 3com Audrey, I have been playing around
with QNX 6.0. What I noticed is that when playing MP3s that are on a
shared drive connected via fs-cifs, there is no buffering of MP3s
played through phplay, no matter what the MPEG buffer environment
variables are set to. When the network cable is removed, the file
stops playing immediately. Others have investigated this and
discovered that when MP3s are streamed via http, this does not happen.
What is the interaction between mpegaudio.so and fs-cifs that causes
buffering not to work?