Windows 7 "no connection error" - ALT + TAB not work

I am calling it the No connection error because I figured the error was caused by Windows Explorer having a box pop up above the system clock that says No Connection.

This box, being not very visible will cause your ALT-TAB to not work at all, Minimise and Maximise not work well and windows being inactive when they pop up (e.g. MSN) and cause you to type not into the chat window.

To fix it just click on the power icon, Wi-Fi icon and try to close that box that shows No connection.

Here are things that won't fix it that I have tried:

-locking computer, unlocking
-restarting explorer and then launching it again from task manager
-logging off and back on

Very strange and ANNOYING error/problem with windows 7 >=( especially as it's run pretty nicely over the weeks.