Specifically, I'm talking about the Internet. If you have been working along merrily on the Internet for weeks, months, or years and all of the sudden you aren't able to get email or connect to the Internet, DON'T PANIC. Instead, calmly turn off your computer, shut off your computer and if you have high speed Internet, shut off your high speed modem and router if you have one. Then slowly walk away from the computer and have a nice cool or warm beverage of your choice, take a nap and or a walk.
After about an hour or two, walk back to your computer, turn on the high speed modem and router (if you have one), wait a few moments, then turn on your computer. If the Internet is working, great. If it isn't working, then repeat the steps above and try again.
The one step to absolutely NOT take is calling tech support in the first 12 hours (unless your computer is mission control for the space shuttle or Air Force One). Calling tech support too early often times results in horrid results because many of the 'techs' manning the phones will walk you through steps on your computer that can disable security software and or hardware and put in a real pickle. The best adivice is what I have given to you in the first two paragraphs.