My internet connection (not WiFi) is slow on my 10.8.4 Mac Mini after installing/removing Norton.

Question

I believe I've experienced this problem before, but cannot remember the exact solution. The previous solution was deleting a file in the Mac OS (possibly even the finder? but that sounds worrisome), then restarting.
I am using a Mac Mini 2.5 GHz i5, with 16GB of recently installed (within the last 3 months) 3rd-party RAM, loaded with Mac OS 10.8.4.
Recently, I received a DMCA letter from Comcast (my second), which just seemed impossible to me, so I decided to actually take their advice and install Norton. Why? Because I'm a moron. After all, my network is locked down with WPA2, I have an encrypted Time Machine drive connected to my 3rd Gen Airport Extreme, and encrypt my Mini when logged out (which happens after 15 minutes of inactivity). In brief, there's no way Comcast's letter was correct. But to be sure, I installed Norton.
Almost immediately, crappy internet connectivity ensued. My Wifi signal was always strong, but my computer struggled to connect to the outside internet. So, after a week of wondering, I finally uninstalled Norton (using their uninstall application found online).
Still, my Internet connection was (and is) crap. Here are the steps I've already taken to resolve the issue:
1. I called Comcast and asked them to check on their end. They conducted a reset from their end, which seemed to improve my connection, but only temporarily. It has since resumed a slow connection that sometimes drops out.
2. I tried my network with other devices: 2 iPads, 2 iPhones, and one Macbook Air all have excellent internet connectivity. As I write this, my Mini struggles to load Comcast's speed test site, but my iPhone is pulling down near 30 Mbps.
3. I have connected my Mini to another, neighboring Wifi, and it works like a charm. Fast Internet, no cutting out.
4. I loaded Time Machine, and restored my system to its pre-Norton state. Still, the Internet connectivity is poor.
5. I have created a new network on my Airport Extreme. While my iPhone still pulls down a great connection, my Mini chokes on it.
The only things I can think to do from here is to Factory Reset my Airport (which I don't see as a plausible solution, since all my other devices connect through it just fine), wipe my Mini and start over (not a realistic solution for my business), or throw it out the window entirely, then stomp up and down on it (this won't fix my Internet issue, but I might feel better).
Thoughts? I KNOW it's an easy fix, but I just can't remember what it was. The same thing happened to me a couple of years ago with another Macbook, and it was a simple file deletion and restart.
Thanks in advance for your help.

Answer 1

Alright, I think I might've actually solved my own problem. Here's what I did (for anyone out there with the same/similar issue):
Open System Preferences and click on the Network pane.
Select Airport in the list to the left and click the minus button below to temporarily delete it.
Restart your Mac.
Go to the Network section of System Preferences again, this time pressing the plus button towards the bottom of the window.
Select Airport from the Interface menu, leave “Airport” as the default name, and click Create.
Select your WiFi network, and enter your password.
My speed is back up to speed, so fingers crossed that this works!