Can connect to wi-fi but only some sites/apps will work

I'm not able to use the Internet through my Linksys WRT54G v6.0 router on my Nexus 7, running Android 4.2.2. Before Sunday everything was working fine with it. Now, only a few things on the tablet are able to use the Internet -- everything else times out and gives an error when I try to load something. I don't immediately get an error when I try to access or update a page or app. It hangs for about 10 seconds, and then tells me that it can't load.

What does work:
-I can search Google using the built-in Google search app.
-A few sites will load in Chrome (it seems like the sites that I don't visit will load. This makes me think it's a caching issue, see below)

What doesn't work:
In particular,
-Facebook app
-Pandora app
and
-Pretty much any other app that requires the Internet.

What I tried:
-At first, I thought it might be a DNS issue. So, I downloaded SetDNS from Google Play and changed my DNS (I was then using Google DNS 8.8.*) to OpenDNS. This didn't fix the problem.
-I then thought it might be a caching issue, but thought it was odd that Google searching in the dedicated app (not sure what this is called) would still work since I still use that regularly. So I tried removing local data and cache in the Facebook app, but this did not fix the problem in the app. I also tried the same method for Chrome by removing the local app data and cache, and still no luck.
-Hard resets of my modem and router.
-Hard reboot of the Nexus 7.
-Forget the Wi-Fi connection, and re-connect. Still the same behavior.
-I checked if my router (Linksys WRT54G) or modem (Actiontec M1000) have any firmware updates available, and they don't.
-Other Wi-Fi networks will work just fine.
-Other computers can connect to and use the Wi-Fi (and wired) connections that I'm having trouble with my Nexus on.

 

This fixed the problem! I changed the IP address to something that was much higher in the subnet than what was being used by the other computers on the network (eg., the DHCP IP range was 192.168.0.2-192.168.0.50, so I gave it 192.168.0.12 for its address).

I checked my modem's Port Forwarding settings, and I noticed that a lot of the rules were defined for the IP address that the tablet had. One of those rules was for port 80 (HTTP), so I'm guessing that was what was causing the problem. My DHCP configuration must have changed. I haven't tested this theory yet.