internet dying on me !!!

Ok I'm in dire need of assistance, few days ago I noticed a degraded in my internet connection, pages taking an age to open, being disconneted from online games....
Today I logged into swg & noticed straight away, my ping was it usual low 60's, but packet loss which usually is 0% was flucuating between 20-50% never going below 20%
I logged into my second account on 2ns PC & bam same thing on this pc, high packet loss
So I phoned up my ISP British Telecom, after 30 mins chatting to the indian dude it was decided the problem wasn't with them, he also said he could advice me as too my router as it was a Netgear (router is a Netgear DG834 v2) & third party, they did tell me to delete temp file, history blah,blah blah
So next I phone up netgear, the ask few details, how many pc's do I have linked, what was the connection speed between my 2 pc's, after another 40 mins they said problem wasn't with the router..
I have done virus, spyware & adware scans, but to no avail, i'm totally flumoxed & I'm seeking help !!!

Also I've had the router 7 month hitch free...

Ping each computer, the router and the modem see if there is packet loss.
Then ping quite a few web pages.
If you only get packet loss on the internet side then thats the prob.

I know basically what my problem is, high packet loss resulting in near zero upload speed...downloading & overall latency are fine...

I've been at British Telecom (ISP is BT/Yahoo) today, they say my line is perfectly fine, but they referred me to Yahoo, who will get back tp me within 48...

I've done all suggestions, including putting my router back to factory default firewall settings, the BT guy seems to think its a firewall problem I'm experiencing, but nothing seems to have budged my problem..

Could it be my extension cable from phone line to router? probably clutching at straws, can't be either of the Ethernet cables running from router to my 2 PC's as highly unlikely both would become busted simultaniously...