Here's my network:
[pre]+-----+                          +------+
|    |          +---+          |      |            /--\
| 4  |-----------| 2 |----------|  1  |------------|0 |
|    |          +---+          |      |            \--/
+-----+            |            +------+
                    |
                +-------+
                |      |
                |  3  |
                |      |
                +-------+

0. Internet
1. Windows machine (Dial up, ICS)
2. 4-port ethernet switch
3. My box (httpd)
4. My (other) box (paperweight)[/pre]

Basically, the Windows machine is supposed to forward :80 to 3, but it won't. It can resolve 3's IP to "deadmeat" (my hostname), but ping's cant be sent. I'm guessing that the network card is being a bitch about opening connections to foreign local (hehe, oxymoron) boxen, or sending UDP packets.

Anyone think I'm right / wrong?

Maybe firewall settings are interferring....

Not to complain about your network design or anything, but i disapprove  :) .....

No firewalls inside the network. I don't care if my brother's machine dies, so no firewall outside of it either.