Ubuntu – Ubuntu 14.04 Intel 7260 AC Wireless driver does not work properly

I have dell xps 13 developer edition with ubuntu 14.04. Actually when I bought the machine it came with ubuntu 12.04. Before upgrade to 14.04 the wireless driver was running perfectly. After upgrading to 14.04 the driver gets in broken mode. I can connect to saved networks but if I plan to connect to an unsaved network it does not work. When the qui gets in trouble I give a try to terminal by typing:

$ iwlist scan

The response is:

lo        Interface doesn't support scanning.

virbr0    Interface doesn't support scanning.

lxcbr0    Interface doesn't support scanning.

wlan0     Interface doesn't support scanning.

My driver info:

$ sudo lshw -C network

  *-network               
       description: Ethernet interface
       product: Wireless 7260
       vendor: Intel Corporation
       physical id: 0
       bus info: pci@0000:02:00.0
       logical name: wlan0
       version: 6b
       serial: 7c:7a:91:8c:df:fc
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical
       configuration: broadcast=yes driver=iwlwifi driverversion=3.5.0-48-generic firmware=22.0.6.0 ip=192.168.2.237 latency=0 link=yes multicast=yes
       resources: irq:58 memory:f0400000-f0401fff

I am really in a big trouble. I can connect to any wifi network except saved wifi networks. If I can not find any solution I will downgrade to 12.04 again.

What is the proper way using this driver with 14.04?