Dlink DSL-2740B connection issue

HI, I have trawled for a similar problem but can see anything so that is why i have posted.

I can connect to pretty much all networks, including public wifi points, except for the network at home. We have 3 laptops in the family, the Dell laptop conects with no issues but both the Acers are the same in that they can get an excellent signal but can't load any internet pages. I have a d-link router and XP works fine with it . If I load the D-Link DWA-140 adapter all works well, but I dont want to have to buy another one for my other computer.

Any ideas, thanks?