Network has lost WPA-PSK authentication

My laptop computer has been working with a wireless Linksys router for some time (months). I'm using WPA-PSK network authentication and TKIP data encryptioin.

It suddenly stopped linking to the router. I go to Wireless Network Connection, right click on it go to Properties, click on the Wireless Networks tab, click on my Network SSID in the list and click on Properties. The Network Authentication drop down has only Open or Shared, no WPA-PSK. The Data Encryption drop down only shows disabled and WEP.

How do I restore the WPA authentication and encryption?

 

I could be wrong, but I think the "Shared" label on your computer might refer to the PSK.

PSK stands for "pre-shared key", so I would think "Shared" is just shorthand for that.