Sounds like a default gateway, subnet or DNS problem then. Make sure all those network settings are correct.
What am I looking for with those settings? Sorry, I'm not very experienced with routers, everything is just set to the defaults (and is working fine for everything else).
Under Settings tab on the L3+
Netmask = is usually 255.255.255.0 (but can be different)
Gateway = your routers ip usually 192.168.0.1 or similar 1.1
DNS = 8.8.8.8.
On windows pull up a termianl screen and type IPCONFIG
look for Ethernet #
And should show you
IP address (which will be the address of the windows machine you are on)
Subnetmask (this is the netmask and you should set the netmask on L3+ to what the pc shows)
Default Gateway (this is the gateway to the router and you should set the gateway on the L3+ to what the pc shows)
Set DNS to 8.8.8.8
Save it and reboot the L3+...