Alright, I'm stumped. I've tried it all.
At our office, we have Telus ADSL.
We have five computers and a network printer. Prior to me starting there in January 2002, the computers were all networked through a hub, two of these computers were online and the other 3 were just shitboxes for typing letters.
I set us up with a Linksys 4 port router (BEFSR41). Used the uplink to go to the hub and so everything's been fine.
About two months ago, our connection just went to hell. Essentially, we had very intermittent access. I'd be online, go to another site and have lost connection. The connection between all of the computers and the router was fine, all internal network traffic was fine, but the router was having a hell of a time keeping an IP (I determined this by checking the web utility and releasing and renewing the WAN IP - it would usually take a good minute or two to get an IP if it could get one at all).
I figured it was Telus, but just to test, I plugged one of the computers directly into the modem and wham bam...perfect connection. I plugged the router back in...back to a crappy connection.
I then figured it must a hardware problem so I tried replacing nearly everything - and I mean everything...I replaced all the cables, the modem, the router, everything. Then I plugged in a dinky little D-Link router (DI704P) and suddenly everything was fine. Obviously I was confused, but I wrote it off to the Linksys having kicked the bucket (even though I had tried a brand new Linksys wireless router and had the same problem).
Then last week...it started again! It's the EXACT same problem. I tried plugging in our old router and it's doing the same thing. I tried going directly to the modem...no problems.
I haven't changed anything hardware wise. I recently installed Norton AV Pro on all of the computers, but I doubt that would effect anything. Also, it worked impeccably after that for a few days, so that also makes it seem unlikely.
Speaking of antivirus...I called D-Link to ask them and at low level tech support, they suggested I disable my firewall (which I don't have) or that we might have a virus...Blaster specifically. I already dealt with the Blaster issue when it started, so that wasn't it, but I followed their advice and grabbed Stinger from McAfee's website.
I've ran it on four of the five computers and so far 2 of them had SirCam (which I had previously thought had been cleaned...and wasn't picked up by Norton...craptacular program that it is) and one has had a lingering problem with Nimda (try as I might...it won't go away). The fourth came up clean.
Based on these results, I figured I'd run a different test and tried connecting JUST the clean computer to the router to see if that might solve the problem, but it seems to STILL be having the same issues. This means that it was JUST that one computer connected directly to the router which was connected to the modem, no other computers at all.
So basically, I've ruled out hardware, cabling, Telus (I called Telus and they said that we're fine - particularly because when we connect directly to the modem, it works fine) and viruses.
What the fuck am I missing? It can't go on like this...there has to be SOMETHING that will work.
Geniuses, unite and save my ass.