HP laptop can connect to network but not internet

[dopesickbadfish]

I am a relatively new Xubuntu 11.10 user. I have an HP Pavilion dv6 (dv6z-6c00). I had no trouble connecting to WiFi network or internet until I moved 2 days ago and Comcast provided a new modem (Arris TG862). Trying to connect to the internet via Linksys WRT120N router.

I had issues connecting but thought it was because it was a new house and signal was weak in my bedroom. I have had no trouble connecting to the LAN/WAN but have had very poor connectivity to the internet. Typically it would connect for about 1-2 minutes and then drop. Tonight (about 48 hours later) I have had 0 internet connectivity.

Here's all the stuff I've tried today (I've spent hours on this!!!)

* Updated router firmware
* Installed WICD Network Manager
* Tried changing the broadcast channels to various frequencies/channels/automatic -- no change in connectivity
* Updated driver (Realtek RTL8188CE 802.11b/g/n WiFi Adapter) -- this improved signal for available networks, and boosted internet connectivity for about 20 minutes, but now can't connect to internet at all

I also have a USB network adapter -- TP-Link TL-WN727N
I tried this, and at first connectivity was boosted significantly and I could browse normally, but now using it has no effect/change

I can access both the internet and the network fine on my mobile device & another laptop.

Is this a hardware issue, a Comcast issue, or something else I'm totally missing?

ANY advice is greatly appreciated!!