Frequent and short internet disconnection

[masterlargo]

My internet keeps disconnecting every 5 minutes or so. I usually get it fixed by going into Network Diagnostics, selecting it, and clicking continue a few times. I don't know why that works but it does. What I see in the Network Diagnostics panel when it just went out are yellow lights next to ISP, Internet, and Server, as opposed to the usual green light.
I've noticed that it happens a lot more frequently when doing tasks that require a bit more internet (though never in excess of my connection speed).

It's not the internet, the router, or even the airport expresses I have in my house, since the Time Warner guys came by today and did a full check of everything. They even replaced the router. I thought it would have fixed it, but still no luck. I tried resetting the DHCP license and rebooting everything, it still happens. It's very aggravating when I'm trying to download something or buffer a video.

Is there anything I could try to fix this very annoying problem?

I'm using a late 2006 iMac, running Snow Leopard.

 

[allan.nyholm]

I see the same thing after surfing using Safari 5.0.1 for an extended period of time. My router simple rolls over and gives up. I've been using Firefox now for a week and nothing has happened. In the release notes for Safari 5.0.1 there was something about Safari's prefetching causing some routers to give up and this being fixed.This has not been fixed to my understanding.

I have also switched to a completely new router from my ISP thinking it was that. I even purchased a new AirPort because I thought that the one I had was faulty after resetting and everything.

 

[masterlargo]

I don't think it's the browser, because I used both Safari and Firefox and it happens with both. It also happens when I'm using other applications, like games or skype or browsing the iTunes store.