Thanks for your replies on this, very helpful!
I upgraded the firmware on my router, didn't help.

More information:

It's also not working on my girlfriend's wireless network at her house
35 miles away from my own (just so no one thinks we share a network
LOL)
I'm there now, and I just restarted my laptop and connected. I checked
my email, then walked away for 5 minutes. When I came back, it hadn't
gone into standby yet (I left the lid open on purpose) yet the
connection was dead.
I just restarted AGAIN, and I'm online as we speak (of course, by time
time I finish this message it may be dead again and I'll have to
retry!)

So, now I'm inclined to believe it's:
a) The wireless card's drivers and/or config
b) Firewall or other software, possibly virus

The thing that's leading me more towards B is this:
I recently installed AOL's Active Virus Shield. At roughly the same
time the connection went dead 5 minutes ago, AVS warned me that the
"Busky" virus was detected and did I want to delete it?
This is the first time that AVS has gone off at the same time that my
connection went dead, so perhaps it's not the virus itself, but AVS
acting as a firewall?

Bill, I will try the steps you recommended. Thanks for any further
replies and assistance.
Bill Kearney wrote:
> > Any thoughts on what this could be?
> > At this point I'm entertaining the following notions:
> > 1) short circuit in the ethernet cable from router to modem?
> > 2) wireless router is failing?
> > 3) wireless card is failing?
>
> It's option 3, but probably not a hardware failure. Driver and/or
> configuration.
>
> The common element here is going into standby, right? There are lots of
> cards and their drivers that have had great trouble with coming out of
> standby mode.
>
> Do this, when it's working pull up a CMD prompt and type "ipconfig /all" and
> note the information it shows you. Put the laptop into standby, move to the
> other location and type ipconfig /all again. See what (if anything) is
> different. Then type "ipconfig /release" followed by "ipconfig /renew".
> This will release/renew the DHCP networking information. Then use ipconfig
> /all to show it again. See what's different.
>
> I'm guessing it has everything to do with your laptop going to sleep and not
> reconnecting properly on waking back up.