Windows 7: Seen this alert a few times- can anyone decipher?

As best I can determine, somehow your computer made contact with a website called "the-independent<dot>info" at IP Address 178.162.170.58 through Port 80 on your machine. When I tried to visit that website, my antivirus blocked me and said the website contained malware. So whichever antivirus or antimalware suite you're using, it worked by blocking access to the website.

An IP address search shows that an organization called RIPE Network Coordination Centre, Amsterdam, The Netherlands, controls all IP addresses from 178.0.0.0 through 178.255.255.255 and last updated their information on Sept 24, 2011.

http://whois.arin.net/rest/net/NET-178-0-0-0-1/pft

An internet search for RIPE Network Coordination Centre shows them to be an apparently legitimate organization. They are "...one of five Regional Internet Registries (RIRs) providing Internet resource allocations, registration services and coordination activities that support the operation of the Internet globally."

RIPE Network Coordination Centre

X-notifier is a webmail notifier and supports Gmail, Hotmail, Yahoo, AOL, Daum, Naver, Nate, Paran and who knows what else. I've never heard of the last four but presumably they are webmail providers outside of the United States. And here's my personal opinion FWIW. When you tweaked your X-notifier settings, somehow or another your computer made contact with RIPE. Because RIPE is in the business of providing IP addresses and domains, and maybe some of the hosted domains have questionable content, RIPE was flagged by your antivirus as being dangerous. Just a guess.

Personally, I'd want to keep receiving those alerts. But I'd also contact the author of the addon, explain the situation, and see if they have any additional info. Maybe they have a glitch in their code or have received other compaints.

WebMail Notifier - Notifier for gmail, yahoo, hotmail and more

Flush the DNS cache ... Right click on command prompt, run as Administrator, then copy/paste ipconfig /flushdns, press the enter key.

what does this accomplish? and how do 'right click on command prompt?'

Type cmd in search box, right click on cmd.exe > Run as administrator

Flush DNS - What's My DNS?