not 100% sure what you need to do, But you may need to have specific files or plugins that you may not, I know you can open most pps files in openoffice ... I dunno about a PPS movie though.
Try using Synaptic to make sure you have all Lib files and/or Gstreamer files you need (google will let you know what those are).
Also are you using a specific PPS viewer or are you using TOTEM to view it? ... I do know that Totem has a plugin to work PPS.
Last thing I can think of is a problem I had. I was using my Zsnes emulator, and it had no sound. I simply opened terminal, put in ZSNES
(to run) and added -ad sdl
(to initiate sound), so maybe you could do:
name@computer:$[ppsviewer] -ad sdl
These are all just shots in the dark though, but I hope you get some info from it. Good luck.