Slowed internet on Lion

Hi, I recently got an iMac in August and it has been blazing fast, but over the past few weeks, the internet has slowed significantly. I have updated firefox and there are no new updates for my mac. I save everything on an external harddrive. Videos over 2 minutes have problems playing, yet I can play them easily on my cell phone or on my ancient PC laptop. Since it has slowed, I have searched for others advice and have changed my "Configure IPv6" to Link-local only and even put in new DNS servers (4.2.2.1 and 4.2.2.2) but nothing seems to work. All other software seems to run at high speeds as usual, something is holding back my internet though.

System specs:
Mac OSX Lion 10.7.2
2.5 GHz core i5
8 GB RAM
500GB harddrive


Looking forward to your responses, thank you.

2 things to start with, check your Console Logs
and plug it in via an ethernet cable and see if the problem persists.

Sure, what am I looking for in the console logs?

Run it open while browsing the web, sending email and the like. See if anything is reporting problems.

Nothing with the console logs, I'll try plugging directly in later.

It seems like about 5 minutes after I turn my computer on, it runs fast, and then appears to just drop out, at least in terms of just loading/downloading bigger files. Also, if I wake my computer after it goes to sleep, it takes a while for the signal to connect, I don't know if that has any correlation or not.

Ok, the other App to look at is Utilities > Activity Monitor
You want to sort the list by CPU, and see what Apps are at the top of the list, when it slows.
I'm guessing scanner software.

Looks like all of the ones at the top of the list are activity monitor, firefox, and adobe flash plugin which add up to only a maximux of 10%. Unless I run a game or other software, but of course that obviously uses more CPU. The graph of the network shows many green spikes of data received, but a flat red line of data sent, is that normal?

Yes, that sounds very normal. The red line is sent packets so it will only spike on an upload.
The many Green Spikes are all the download packets.

So it doesn't sound like its a process going out of control.

Looking like we're isolating it to the WiFi, so you really need to see if the problem remains when switched over to Ethernet and turn WiFi off.

How much RAM do you have?