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.
