Unable to connect to wireless network following upgrade to 15.04

I upgraded my Dell Inspiron 7547 from Ubuntu 14.10 to Ubuntu 15.04 today, and I am now unable to connect to wireless networks.

I can see the wireless connection I am trying to connect to, but I am unable to connect. The connection times out without presenting an error message. First I tried forgetting the network and putting the information back in manually. I then tried disabling the wireless security on the router (Linksys E900) and reconnecting and had the same issue. I also tried connecting to a WiFi hotspot from my phone and had the same issue. The wireless connection from the router works fine on Windows 8.1 and my other wireless devices.

Any advice on what I should try next? What additional information can I provide to help?

Per comment, here is the output from running the wireless script: http://pastebin.ubuntu.com/10875310/

I have been having similar issues (same wireless card). Here is what I did to fix it:

sudo service network-manager stop
gksudo gedit /etc/modprobe.d/iwlwifi.conf

Add options iwlwifi 11n_disable=1 to file, save, and close. Then:

sudo rmmod iwlmvm iwlwifi 
sudo modprobe iwlmvm iwlwifi 
sudo service network-manager restart

This will inactivate Wireless N so network speed may be affected.

If that doesn't work undo what you did by:

gksudo gedit /etc/modprobe.d/iwlwifi.conf

and delete the last line (options iwlwifi 11n_disable=1) and everything will be back to the way it was before.

Evan's solution wasn't working. But, I have fixed the wifi issue by upgrading my linux kernel to 4.x as mentioned in the below post - Install Linux Kernel 4.0.3