I have a linksys wrt54g ver 6 and I'm running DD-WRT v23 SP2 (09/15/06) micro. Also running Leopard 10.5.1 and eyeconnect 151 trial.
I didn't do anything to my router settings to get this to work. I have media server enabled in the xmb. My PS3 doesn't have any troubles seeing or connecting to the media server. I have used null rivers medialink and eyeconnect. It also see Azureus although it doesn't seem to work real well with that. I believe that is a design issue with Azureus. I have uPNP enabled in my router thus the PS3 automatically sets it firewall settings. I DO NOT have apples firewall running. I do not have any problems with wireless settings on the PS3 AND I'm running a hidden SSID which the PS3 connects to just fine. As a matter of fact the ONLY issue I seem to have right now is streaming HD content over wireless. It seems to be kinda jerky which would make sense since it's kind of high bandwidth. I have not tried it using a wired connecting to the PS3.
If you are running wireless, maybe the signal isnt good enough. With dd-wrt firmware on my router, I am able to go in and adjust the signal of the wirelss, maybe that has helped me some. I did do some adjusting to it but NOT for eyeconnect or any other media streaming app. I only played with that setting to see if I could get a better signal to another laptop.
I am a bit confused though. Just to clarify, does your MACs wireless die or just the PS3s? Are you turning mediaserver off on the PS3 or on your mac via medialink or eyeconnect?
If I understand correctly, your MACs wireless is dying. In that case, I can't imagine this has ANYTHING to do with the PS3 OR your media server software on your mac. Coincidental, yes! I do from time to time have issues with my router losing an internet connection for some reason and I have to reboot it. Maybe this is what's happening to your router, I don't know.
As mentioned, try turning on and off a few times the media server on the PS3 WITHOUT ANY media server apps running on your mac! Just cruise around the net on both machines and see if you maintain connectivity. Then ONE BY ONE, start the media server on the PS3 first...try internet again on both....then start the media server app on your mac.
If AFTER you start the media server on your mac, your macs wireless dies and you lose connectivity to the net, then I would suspect the router at that point. If it's anything like my connectivity issues at times, it's the router.
My router issues my be linked to when I play around with QOS and other settings to optimize my network but I always end up turning those off because I can't seem to get them to work very well with this PIECE OF **** ATT DSL SERVICE I have!
Bottom line is that I am having NO issues streaming data to my PS3 with my WRT54G router. Maybe you have and older revision which DOES have issues. Mine is about 1 year and a half old. If yours is older than mine, then maybe it IS your router.
The reason I'm posting is that I noticed a few spouts about this router and although not the best one in the world, it's doing fine for me and my PS3. You might want to check their site to see if there's a firmware upgrade for your router. below is a link... I'll check back to see if you've made any progress.... Maybe I can help out more.

Dam...did I just type all that ****??
http://www.linksys.com/servlet/Sate...rapper&lid=3740137401B01&displaypage=download