LOL! I had the exact same problem, i just got my ps3 headset yesterday and was wondering why i was constantly being logged out of psn, to the point i thought the psn was under attack again. Then i figured out the headset was causing the problem as this didnt happen when i tried logging on with the headset off.
i tried switching channels on my router (cisco linksys e3000) from auto to every single channel... Nothing worked. I tried using a usb extension, like you said and... Voila! Problem solved! Thanks!
I actually used the rockband usb extension, so yeah it's not nice to look at, but hey, it works.
I actually had the same exact issue as the OP tonight for the first time, but I did just install a new Asus router recently. So need to expirement with which channels work best. Thanks to all that posted in this thread.
Actually I have an app on my Mac that analyzes all WiFi networks in any given area, tells you what channel they are on, etc., I now am wondering if when I turn the headset on, it would show up? If so, I can find out the exact channel it uses.
I will post back if I can find the channel.
But go settings-network settings-media server-disable. I had solid performance after that. Failing this I was going to change my wifi channel on the router, but seems to be fine now.