Two machines on wireless, one disconnects randomly, other doesn't

Hi,

I have two machines - a PC and a laptop, both running XP. The PC has
an older DLink b network card, and is connected to a DI-524 wireless
router. It works rather well.

My laptop, which I bought used a few days ago, is another story. It
disconnects every once in while. It has a DLink g card, which is brand
new.

When the disconnection occurrs, Windows shows my connection as active,
but I can't even ping my router.

Sometimes, after a while, things sort themselves out. Sometimes, I
have to repair the connection for the laptop to connect again. During
this whole disconnection cycle, my PC remains online.

I have seen several similar issues on the web, but none seem to fit
this description. Any thoughts?

Thanks,
Eyal.

eyal.susser@gmail.com

More info:

-Driver is latest version.
-Router firmware is latest version.
-Boh machines on static IP (haven't tried to recreate with DHCP yet).
-Disabled Windows Zero Configuration, working with Dlink utility to
configure.
-Utility shows 100% Signal on both counters.

And, most importantly:

This seems to happen only if I have MSN Messenger signed in.

Any thoughts?