Am I doing something wrong, or need to change some settings here.

I have a 4TB RAID5 NAS unit with built in media server at my house which is accessed using 4 devices, my PS3, my Samsung LED TV (which has built in Divx and wireless), my Netgear EVA2000 and my laptop. Every single device connects to the NAS wirelessly and every single unit runs flawlessly... except the PS3. Whenever I play a movie through the PS3 it stops every 3-5 mins to buffer for a few seconds.

Now normally I wouldn't use the PS3, however it can play more formats than the TV and it can pause the movie which the TV can't. The Netgear media streaming device is in the bedroom (which is even further away from the WAP) and I don't want to have to move it into the living room just to play certain movies.

Its not like I'm trying to play MKV Bluray rips here, just 1.4-2GB DivX and H264. Surely the PS3 has better functionality than this.

Dude, if I had your setup, I could die a happy man. That or Kim Kardashian, whichever works. 

wait a little bit before starting the movie/video. The PS3 doesnt have to receive the content, decode it, and display it. Takes more than 20 seconds. Pause the stream at the beginning of the video, wait about 2 minutes, then start.

Yeah, despite your amazing system, you are doing something wrong. Mine is fine.
However, on certain shows, there is a stuttering at almost exactly at the same point.
Example: On metalocalypse, it stutters everytime Nathan Explosion's bike pulls away from the bike group in the opening. It stutters for like 15 seconds and then everything plays normally again.

Are you running it via PS3 media server or tversity? Also theres alot of configs throughout the internet that can help you with the wireless setup. Thridly, the PS3 dosent support .n routers, or well, the speed they can produce wont make the stream to the PS3 go any faster.

I've tried pausing the movie for a few minutes and it still does the same thing

No Tversity or PS3 media server through a PC. The NAS has a built in uPNP & DLNA media server so from the Xross Media bar i just browse to the video icon which shows up NAS as one of the options as it's detected the media server automatically. From there I just browse the contents and select the movie I want to play.

Have you tried using windows media player sharing to stream video?

I used the PS3 media server program briefly which I got working but never used much as I got the NAS unit shortly after and that's worked for most things as well as I need it to. The PS3 streaming thing is just something I've only just got sick of and wanted to see if anyone had any suggestions.

Windows Media PLayer allows wireless streaming to the PS3. It's by far the least complicated way to watch videos of all most types on your ps3.

wait...so you can stream video just fine, but you want to be able to stream with the media server function? Just use it the way it works.