I've checked recently this problem. and found someone with the same issue. My roommate just brought home a PS3 for us to test. The wireless does disconnects very often with our Linksys router. (WRT54G version 5: latest firmware). Other wireless devices, connects smoothly but not the PS3, ruling out the router.
I've post somewhere on this forum what could be causing this problem. I work for Linksys and checked on this issue but no found no prduct known issue regarding the wireless connection with PS3. I've also checked if someone has filed this issue as a possible product issue (well, it's a shame to tell you that Wii has an issue with WRT's) but there are none.
My theory would be a wireless interference. Generally, the problem is observed only when using the bluetooth controller and the wireless at the same time. Bluetooth and Wireless Routers (B, G and N standards) operates at 2.4 GHz like most wireless products are (cordless phones, wireless baby monitors, wireless game adapters, etc). It has been known that bluetooth interferes with wireless signal coming out from B, G and N routers. That may explain the wireless disconnection.
As for Port forwarding, Port Triggering and DMZ setup on the router. These settings has nothing to do with the disconnection as long as configured propery. Configuring port settings will not help with the wireless disconnection issue. The main goal would be fo first fix the wireless connection to the router. Once established, you can continue with the port opening.
Could you please help me testing my theory. The test would be trying to check the wireless disconnection when the bluetooth comtroller is not used. Just check it out.
I wish and hope I'm wrong. :-[ ...
