0005834: iwlwifi driver for Centrino Wireless-N 1000 slow and unusable after upgrade to CentOS 6.3

I updated to CentOS 6.3 yesterday. Before the upgrade the integrated Centrino Wireless-N 1000 (wlan0) worked acceptably well. After upgrade, the wlan0 interface is largely unusable. There seems to be driver issues. <br /> I'm using NetworkManager and have been for several years with few issues.