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.