I'm a little late to the party, but I've finally started to figure out the whole multimedia bit, and I was able to install BetaPlayer on my X50v and use it to stream videos off my desktop machine using Wifi. Most worked just fine through this setup, and looked quite nice. I found a few of my higher quality DivX files (640x480, 194kbps) would need occasional pauses to buffer while they were playing. The one I copied to my SD card to try it out played without any interruptions, so I'm wondering if there's a setting in BetaPlayer I can change to reduce the need fur buffering?

Don't know if this helps, but for movies, maybe try to set the memory setting slider to give the axim as much program ram as possible. Also make sure nothing is running in the background to eat up that ram too.