On my D-Link DGL-4300 router I have this option called "Group Key Update Interval" which is set to 3600 seconds (1 hour). I currently have it rigged up for WPA2-AES and every hour my notebook will disconnect for several seconds some times several minutes before reconnecting, so obviously these are linked somehow.

Now, I tried looking all over the Internet and wasn't able to find enough information about this and was wondering if anyone here can shed some light.

1) What is the option for? What's it do?
2) What's a good interval to set to remain uber secure?
3) How can I lessen the disruption it causes?