I haven't been able to get videos to work either. I'm using MediaLink on my Mac. My PS3 can see and play all my videos. The 922 can only see the mpg videos. They show up in the list but when I try to play them it goes to the screen like it is going to play it then chews on it for a while and then back to the list.
I use playon and I am able to play most of the files. Now one thing is playon transcodes all files to "MPEG-PS" (mpeg program stream) at 480P. I have also used ps3mediaserver and I was able to play MKV files by transcoding it to "MPEG-TS" (mpeg transport stream).
What kind of file you are trying to share? If you don't know then following is a really good program to find information about audio/
MediaInfo