I lose contact with the same sites.
www.trickery.net which is hosted on the UK2 servers and
www.spv-guild.com which is hosted on the I-websolution servers. Iirc Wireplay.co.uk also falls over, but overclockers.co.uk works perfectly as does bbc.co.uk. I don't have MSN installed so not aware if I lose access to it when things fall over. I have tried pinging the addresses when the website wont open and it can't ping em. Haven't tried tracert'ing them though, I'll try that when it happens again.
Off the top of my head I'd say I get cannot find site on just over 50% of the sites I try when I'm experiencing the disturbance in the force.
I really don't think it could be the router, as its been fine for 9 months. However, I unplugged it earlier and I'll see if the problem still occurs.