depends on what kind of format you're playing
normal resolution movies usually play well when you stream, hi-res is usually a bit too heavy to pull off by the router.
Also I've hear that the O-Play suffers some problems with networking.
I dunno, but if it's also capable of doing UPnP streaming you might want to install mediatomb or something
you can try this how-to: http://wl500g.info/showthread.php?t=13963
especially look at this post since it's the working how-to: http://wl500g.info/showpost.php?p=138068&postcount=19