TCP prohibited with Netgear router?

I used to think this was a more general problem, but I've narrowed it down,
I think. I was going to replace a USR8054 with a Netgear MR814v2 yesterday,
but I still have the USR. Each has four (10/100?) ethernet ports, and an
802.11 transmitter -- USR is b/g, Netgear is b only. All machines in the
house except for mine can get on the net (and my VMware "machine" can).
Since the VMware machine (running Windows 2000) uses the same NIC, cable,
and router port as the Linux box, that narrows it down to the Linux TCP
stack. Right now, both routers' transmitters are turned on (channels 1 and
11), and the laptop I'm currently using is associated with the Netgear
router. I've verified that association through 802.11b, and daisy-chaining
through a dumb hub, and direct connection all work.

Right now the network looks like this (but I'll most likely try different
topologies until it works):

(internet)
|
+-------------+
| cable modem |
+-------------+
| <- Netgear's "WAN" port
+------------------+
| Netgear NG814v2 |~ ~Thinkpad (works)
| 192.168.1.31 |
| (static address) |
+------------------+
| | | |
| | | +-
| | +- Linux 2.4.22 (doesn't work) with W2K in VMware (works)
| +- Windows 2000 (works)
| <- USR's "WAN" port
+---------------------+
| USR 8054 |~
| 192.168.1.25 |
| (DHCP from Netgear) |
+---------------------+
| | | |
| | | +-
| | +-
| +-
+-

I also have a dumb 8-port hub with some more devices that's not hooked up
right now, although with a second router, I may not need it. I manually set
the Thinkpad's gateway to whichever router's radio it uses.

All of the servers on the Linux box -- SMB, HTTP, DHCP, SSH, etc. -- are
accessible from other machines on the LAN. I can ping outside hosts, and
name resolution works, but I can't use POP, NNTP, FTP, HTTP, or likely any
other TCP-based service, to access any outside machines. I don't know of
any UDP-based services to try.

Does anybody know a workaround, or if I have the diagnosis correct?

-eben