iChat And New D-Link Router Problems

Folks,

I really need a helping hand with iChat. I've posted some problems here before which you were kind enough to help me out with but I am at wits end tonight. I just bought a new D-Link EBR-2310 Wired Router (Hardware Version B1 and Firmware Version 2.01 - the very latest version). I'm completely up to date on my iMac running Mac OS X 10.5.7 with every software update known to June 11th, 2009 including QuickTime 7.6.2. I have QuickTime Streaming set to 1.5Mbps T1/Intranet LAN and iChat Bandwidth Limit set to 500 kbps.

I use an AIM account which uses port 5190. With my old D-Link Router (DI-604), I had to set up an Advanced Virtual Server for UDP Port 5190 and I also had to disable the "Discard Ping From WAN side" function (which seems to almost defeat the purpose of the security of the router in some ways but I didn't have much choice). Making these changes seemed to fix all the iChat "communications error" problems I was having with the older router. Things seemed to work fine after making these changes mind you, this was under Mac OS X 10.5.6 and I'm now running Mac OS X 10.5.7.

In this new D-Link EBR-2310 Router, I've done much the same thing. In the Advanced Section of the new router under Application Rules, I've set up a new "application name" called iChat and configured Trigger Port 5190 UDP and Firewall Port 5190 UDP - set to "always" but should I have both UDP and TCP enabled or just UDP? I've also enabled "WAN Ping Respond" (again, this seems to defeat some of the security of the router but no choice other than to do this).

I'm getting iChat "communications errors" and just a generally poor connection with whomever I chat with. On their end, my voice will drop out at times and my image will sometimes have a little static in it. It happens with all users on their end (some are AIM users, some are dotmac/mobile me users). After a few minutes of being able to chat, the picture will freeze and a communication error pops up. We have to quit out of our connection and log back in and then it will work again for a while until the same problem occurs.

I called D-Link and they were of no help when it came to using Macs with iChat (iChat isn't even listed as one of the applications in any of the router preferences). They suggested changing the MTU from 1500 down to 1492 but my old D-Link worked fine at 1500. They also suggested disabling "SPI" in the router firewall settings. I haven't done any of this yet as they didn't know much about Macs.

Do I need to disable "SPI" in the router firewall settings? Do I need to configure both UDP and TCP ports 5190 in Application Rules? Do I need to set up some sort of Port Forwarding on this new router? Is there some other configuration I need to set up in this new router? I'm just lost. Darned near ready to do away with the router completely but we have three Macs on our network so we need the router in order for all of us to be able to access the Internet.

Any help would be greatly appreciated.

Thanks,
Gerard