Problems Connecting to Internet, DNS lookup failure

Recently I have been having trouble connecting to the internet with my computer. My school uses a program called cisco nac agent to connect to the internet and originally I thought that was the problem but then I tried repairing reinstalling and uninstalling it several times and the problem persists. When the program is not installed the network is supposed to redirect your web browser to a page to download the nac agent but this does not happen. Instead my web browser (google chrome) just has a DNS lookup failure no matter what website I try to connect to.
This all started happening yesterday when I was browsing the web, (looking at a youtube video I think) and using SSH secure shell when my computer crashed. When I started the computer up again I could not connect, it showed the local area connection that I usually connect to but the nac agent wouldn’t open and let me login like it usually does so I restarted again and what not. I ended up trying several different tactics to make the program work and I ended up doing a repair install of windows.
Now I still can’t connect to the internet and I am wondering if it possible some file got corrupted or if anyone has any ideas how to fix it?

I somehow fixed the problem. I decided it would ne a good time to clean my computer wo i took it apart and cleaned it thoroughly. When I put it back together and started it up, it worked fine.

Interesting problem posted in this thread. I am having what seems to be a similar problem and I'm looking for something other than an accidental solution (although I'll gladly take that if it happens).

I have a relatively new laptop and after a Windows update about 1 week ago, my internet-based applications have difficulty "connecting" when my applications initiate communication with a web site / email server / web-based app domain.

Email (using Thunderbird latest version) - 50% of the times I attempt to send a message, it will not send message after pressing send button with message saying connecting to smtp.(mydomain).com appears. If I hit cancel and press send again or it times out and I press send, 75% of the time it will send. If I have to press send a third time, it sends.

Browser - (using Firefox and IE latest versions) - more than 50% of the time, when I type in a URL in the address box (any URL) and press enter I get the message in the bottom of the browser window connecting to Domain Name Registration and Web Hosting | Domain.com, and I get a blank white screen on the browser and nothing happens after that no matter how much time passes). If I stop the connection attempt (by pressing the 'x' on the right side of the URL address box) click once in the web address bar, then press enter, and most of the time, the site immediately loads. This is particularly problematic when I'm redirected because often times when I'm redirected, everything just stops loading in the middle of that process.

Uncommon applications using internet - they attempt to connect to the internet and most aspects of the application don't have a "stop" feature and I have to wait for a timeout before I get control of the app to initiate a connection.

I connect to a wireless router. Two other people connect via the same router in the same way and use all the same applications. They have had no issues.

I'm am not hardware capable and I'm not capable to taking the laptop apart and putting it back together like one person in this forum did (n309210). The laptop is less than a year old and doesn't get dirty other than using it in a clean office environment.

Any suggestions for a solution?