Wifi connection won't reestablish after logging out

[Moltke]

I am using a usb wifi adpater to connect to my router but not sure if this is the issue or not.  Any suggestions how to fix this?  Thanks.

Have you tried unplugging and plugging it in again the usb just right after logging back in? Untill recently I was using a usb adapter to connect to the internet and that sometimes happened to me too. What I did was that; unplug and plug it in again and voila! It connected. Also, once you're logged back in, does the network interface which the usb uses shows on network-manager?