Thanks for responding to my post, FurryNutz!
I didn't go through the steps you cited because I recently did that after you recommended them to me in response to a performance issue I was experiencing with my router.
After digging into every parameter of my router's (DIR-825) configuration, I determined that WMM had been disabled. I must have done this inadvertently while updating port forwarding for Magic Jack, a couple of days back. After enabling this parameter, everything started to work properly again.