Wow, it sounds like perhaps the extender may be doing some inbound mac or ip filtering. Go into the web interface on the extender and make sure that if it's capable of handing out DHCP that it is not handing out DHCP information that is conflicting with the information that I assume is being given out by the Linksys router.... as a matter of testing, you could try and hard coding the ip address into both the Acer and Dell for the time being, thereby eliminating any potential conflicts, assuming private reserved something like 192.168.1.nnn, subnet mask 255.255.255.0 default gateway the inside edge of the linksys, something like 192.168.1.1 and DNS servers 8.8.8.8 and 8.8.4.4 try it and keep us posted.