I finally tested out PS3 Media server with a full length film today (1hr 40 min) and found myself having quite a few issues.
After viewing the first 25 minutes of the film the video started fast forwarding and the audio began playing very loud white noise, alternating on and off like "SSSS...SSSS...SSSS" etc.
I figured it was just an issue with the video file, so I switched to viewing a different copy of the movie.
Another two minutes in (27 min) it began doing the same thing.
The only solution would be to press Circle and resume the movie (luckily it remembered where I left off).
At around 30 minutes the same thing happened.
My PC is on the first floor and I was in the basement viewing on my PS3, so I couldn't see what the PS3 Media Server was doing, but according to the PS3 nothing was wrong with the connection (the transfer speed stayed between 4 and 9Mbps the entire time, then the glitch would start at 2 minutes after the previous).
I began double tapping X (play/pause) at about 30 second intervals and this occasional pause seemed to prevent the glitch (I went the rest of the film with no issues).
When it was over I viewed the problem areas on my PC, but the videos were fine.
My PMS is version 1.72.0, and both the videos were of the .mpg format.