I am having problem in connecting to wifi. I have dual boot (Windows 7 and Ubuntu 12.04) on my Dell Studio 15. I upgraded to 12.04 quite some time ago (at least one month) from 11.10. Everything was working fine till yesterday. Since yesterday I can see the list of available Wifi connection but does not connect to any or if connects (after hours of trying) then disconnects after few minutes. My wifi interface is Intel WiFi Link 5100 AGN. However the problem is on both Windows and Ubuntu.

Here are outputs of some commands which may be useful for those interested in helping:

~$ ifconfig 
eth0      Link encap:Ethernet  HWaddr 00:22:19:fa:65:bb  
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Interrupt:17 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:794 errors:0 dropped:0 overruns:0 frame:0
          TX packets:794 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:56280 (56.2 KB)  TX bytes:56280 (56.2 KB)

wlan0     Link encap:Ethernet  HWaddr 00:22:fb:d2:fc:ce  
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:239 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:53603 (53.6 KB)

Here is the output for the command sudo lshw -C network

 *-network               
       description: Wireless interface
       product: WiFi Link 5100
       vendor: Intel Corporation
       physical id: 0
       bus info: pci@0000:04:00.0
       logical name: wlan0
       version: 00
       serial: 00:22:fb:d2:fc:ce
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=iwlwifi driverversion=3.2.0-48-generic-pae firmware=8.83.5.1 build 33692 latency=0 link=no multicast=yes wireless=IEEE 802.11abgn
       resources: irq:47 memory:f8000000-f8001fff

My kernel version is

kernel version
3.2.0-48-generic-pae

I also checked this post which was helpful. But I am not sure if what is the exact problem. Any suggestions will be helpful. Should I be changing the firmware/driver? Currently my /lib/firmware has following iwlwifi files

/lib/firmware/iwlwifi-1000-5.ucode  /lib/firmware/iwlwifi-5000-5.ucode
/lib/firmware/iwlwifi-100-5.ucode   /lib/firmware/iwlwifi-5150-2.ucode
/lib/firmware/iwlwifi-105-6.ucode   /lib/firmware/iwlwifi-6000-4.ucode
/lib/firmware/iwlwifi-135-6.ucode   /lib/firmware/iwlwifi-6000g2a-5.ucode
/lib/firmware/iwlwifi-2000-6.ucode  /lib/firmware/iwlwifi-6000g2a-6.ucode
/lib/firmware/iwlwifi-2030-6.ucode  /lib/firmware/iwlwifi-6000g2b-6.ucode
/lib/firmware/iwlwifi-3945-2.ucode  /lib/firmware/iwlwifi-6050-5.ucode
/lib/firmware/iwlwifi-4965-2.ucode

Thanks a lot for the help.