network manager wifi lost

This seems to happen from time to time and not sure why. I will be connected to a wireless network, and then leave my machine and when i come back to it later, the connection is disconnected, so i click on wireless network manager and want to reconnect to my network, only to find that the wireless network is not showing!. Have tried turning wireless switch off and then back on again in the hope that it will detect the wiress network, but nothing. The other thing that is strange is that the option for enable wireless is ticked. Have also tried unticking that and re ticking it, to no affect. But if you go to the hidden wireless network and type your network name in, it will come up asking you for the password, so you put that in, and it connects to the network! if i want to be able to see the wireless networks, i have to restart machine.

This is the screen shot of network manager window.

SUSE Paste

Any ideas why this is doing this and how to go about fixing?