Apparently, I was the victim of the "wireless restart".
I recently put a Windows 7 machine (hardwired) on my network. Windows 7 uses IPv6 which confuses the router and causes it to restart the wireless connections often - thus the dropped connections seen on the laptop. The evidence of the wireless restarts is seen in the router log file.
I turned off IPv6 on Windows 7 and the problem seems to be gone.
Thanks to forums and posts and people like you, as neither the Dlink support team (called three times) and the laptop support team had any idea about how to diagnose or solve this.