I just downloaded PS3 Media Server specifically to play MP4 files (since TVersity and WMP 11 wasn't letting me) and to my delight I actually got it working as soon as I installed the program. However, there is a weird issue where it wont let me fast forward/remind. I can pause fine but if I bring up the time stamp of the video, it just says the length of the video is 0:00:00 and wont let me FF, which is weird since the video is playing. I tested this out with AVI files and I can FF just fine and get the correct length of the videos, so not sure why MP4's are an issue.
Also, I've enabled the chapters option, however when I play from the chapters folder I still don't get any option to skip between the chapters, I have to exit the video and pick the 5 minute segment I want to start at (unless this is how it works)