Caot coect to some websites from one laptop

I'm at my wit's end. Here is the situation.

I have three devices coecting to my WiFi router: two laptops and one Galaxy S2 tablet.

On the first laptop, I can access any web site, no issues at all. On the second laptop, I can only access a few web sites, but not others. On the tablet, I can only access a few web sites, but not others.

I've verified that it's not the ISP. I coected the second laptop directly to the DSL modem and all was well. When I hard-wired the second laptop into the WiFi router, same problem ... not able to access many web sites.

I thought the problem was with the WiFi router, but that can't be the case since the first laptop works just fine when coected to the same router.

Can anyone explain to me why my first laptop works like a dream while my second laptop and tablet both caot access the same web sites as my first laptop while coect over the same WiFi?

Tried shutting down and restarting the router, modem, and laptop, tried ipconfig /release, ipconfig /renew, ipconfig /flushdns ... none had any effect.

I really don't understand how different devices coecting to the SAME WiFi router caot access the same web sites.

Please help and thanks

Eduardo