Can connect to router but not the internet

I'm sure this has been asked before and I've scoured the web for solutions but I'm completely stumped.

Currently if I plug in my ethernet cable to the router I can connect to the internet without issue. If I connect wirelessly I can connect to the router (and also access its admin panel via 192.168.0.1 wirelessly) but it cannot reach the internet.

I tried updating the firmware when this problem arose a few months ago and it fixed the problem. However it appears to be back, and no settings have changed. I went through and re-set all the settings both manually and using a saved config file with no luck.

The network here is rather frustrating as it was pre-existing when this wireless router was added. Since I didn't build the original network I'm not too eager to rewire everything if that can be avoided. It seems to me if I can connect via ethernet cable than it must just be an overlooked setting.

Here is how it breaks down:

DSL Modem connected to Verizon
|
LinkSys Router
|
DLink Wireless Router & LinkSys Switch

The switch is hooked up to 6 printing machines. The LinkSys Router is conncted to our 2 desktop machines and Fiery print server.

When I plug into the DLink directly everything works fine, but if I connect wirelessly I cannot reach the internet. I've tried disabling all wireless security as well as different security WPA/etc with no luck.

I'm stumped, is maybe that the laptop I'm using is Vista? Or is it a conflict with the LinkSys and DLink? How come I can connect via ethernet but wirelessly it blocks the internet?

Stumped

There are 4 IP settings in your computer and your router:

IP address; 192.168.0.20, for example.
Subnet Mask: 255.255.255.000, et cetera

These connect your computer TO your router, or your router to the ISP..

Default Gateway: 192.168.0.1 ( this should connect you to the internet )
DNS Server: 192.168.0.1

These last two connect your computer to the Internet THROUGH your router.

Apparently your IP address and subnet mask are good. The problem is either:
the Default Gateway and DNS settings in your computer do not point to the router;

or, the DNS settings in your router do not point at your ISP.

The tools you need are PING and TRACERT ( in Windows ).

The default gateway is the path through your system to the DNS system on the 'net. If your default gateway is not good, you can't get to the DNS server. Nothing happens until default gateway is right. If you can ping an internet address through your router, your default gateway is good. Typically the default gateway on your computer should point at your router.

Next is DNS server. If your router gives you 3 choices, make the first one your router, the next two DNS servers on the net. Your ISP should be able to provide you a couple of DNS IPs.