Logged off AIM nightly using wireless -- help!

Hi, just a quick question. I'm using a Dell Inspiron 1100 laptop, running the
home edition of Windows XP. I have an SMC wireless card and D-Link router
running from an RCA cable modem. Every now and then, I briefly lose my internet
connection, but it comes back quickly. However, every night while I'm asleep, I
am disconnected from AIM. I am usually, but not always, downloading something
so I assume that means the connection isn't going idle or anything. My roommate
is also connected to the router through a cable, and has not been disconnected
when this occurs. Does anyone have any suggestions? It would be greatly
appreciated. Thanks!

Noel