Linksys Router Losing Connection

I have A Linksys (BEFW11S4) router connected to two computers.

To one directly via crossover cable. That computer has Windows XP Home.

To the other it is connected wirelessly via Linksys (WUSB11) wireless
adapter. That computer is on Windows Me. The router is connected to a DSL
modem (ISP is frontiernet, modem is Efficient's Speedstreem 5200).

Every few moments the connections is lost (for a moment, but enough to stop
most of the stuff like downloads and such). This happenes on both computers,
and when I don't use the router but only the modem it works fine.

This was also happening with another non-linksys router, so I'm pretty sure
the router is in good shape (it is also almost new, and if it means anything
to you, version 4) and the power supply is good.

Here's what I've tried so far and what is set which way:

I've upgraded firmware to the newest version (I have restarted the router
for a few minutes before and after that) but no help. I've been gradually
lowering the MTU to 900. It got better but it didn't stop. Also, the
connection has gone slower.

I've set static IP's on both machines. Nothing.

The connection type is "Auto Detect" because PPPoE blocks the connection,
and Static IP doesn't work (or I set it wrongly).


I would also consider, if everything else fails, using the router as a
wireless adapter. This would be a last resort, and I would like to disable
its firewall in that case so if you know how this is done please tell me.

Thanks!