OK. Thanks Wandering Why. This problem solved last night. It happened when I used my bluetooth device (plug it to one of my USB port) & a message box appeared on top the tray icons says " your PAN network is disable". I enabled it by going to system properties look into hardware, device manager & I found it was disabled. I don't know how it really works or related (maybe somebody who fimiliar with technical can answer) but everythings it back to normal again. TQ guys