Ok, today I finally got around to correcting my network configuration.. which I shall try and outline to the best of my ASCII abilities.

Code:
                 ,
                / \  Internet
              <``X``>
               /_!_\
                 |
                 |   _______
                 |__|       | - 192.168.100.100
                    | Modem |
                    |_______|
                        |
                        |
                        |
   x2 PC & x1 XBox |||||||||||||||| - 192.168.0.1
   ----------------|              | - DHCP On
                   | Wired Router |   Range:
                   |              |   192.168.0.101 -
                   ||||||||||||||||   192.168.0.150
                              |
                              |
                              |
                         ,_,_,|,_,_,
                        (           ) - 192.168.0.254
             x2 Laptops  )  Wifi   (  - DHCP Off
             -----------(   Router  )
                         )         (
                        (,_,_,_,_,_,)
So here's the problem:

Basically, the networking works perfectly; if a laptop is connected to wifi, it gets an IP from the wired router, and the default gateway is acquired properly (192.168.0.1).. same for wired connections.

My laptop is unable to connect to the network while connected through the wifi router when booted into Ubuntu. If I put in my HDD with Windows XP on it, it works fine. Other Linux laptops work fine (Red Hat and Ubuntu). So obviously I must of changed or disabled something on my laptop that is preventing it from working properly. Any ideas?

*** avahi is disabled (multiple ways) could this be a problem? I started the Multicast DNS service discovery (avahi-daemon) and it didn't change anything after restarting networking, etc. ***

This may be useful.. not sure: also, other PCs can't ping my wifi router, not sure why, I think I broke the config on that (I'm on a roll!) but it does work....
# ifconfig eth1

eth1 Link encap:Ethernet HWaddr 00:04:23:92:5c:fe
inet addr:192.168.0.150 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::204:23ff:fe92:5cfe/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2024 errors:468 dropped:468 overruns:0 frame:0
TX packets:33 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:633628 (618.7 KB) TX bytes:3712 (3.6 KB)
Interrupt:11 Memory:c0210000-c0210fff

# iptables -L INPUT

Chain INPUT (policy DROP)
target prot opt source destination
ACCEPT all -- anywhere anywhere
LOG all -- 127.0.0.0/8 anywhere LOG level warning
DROP all -- 127.0.0.0/8 anywhere
DROP all -- anywhere 224.0.0.1
LOG all -- anywhere anywhere LOG level warning
DROP all -- anywhere anywhere

# iptables -L OUTPUT

Chain OUTPUT (policy DROP)
target prot opt source destination
ACCEPT all -- anywhere anywhere
DROP all -- anywhere 224.0.0.1
LOG all -- anywhere anywhere LOG level warning
DROP all -- anywhere anywhere

# ping 192.168.0.1
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.
ping: sendmsg: Operation not permitted

# ping 192.168.0.150
PING 192.168.0.150 (192.168.0.150) 56(84) bytes of data.
64 bytes from 192.168.0.150: icmp_seq=1 ttl=64 time=0.092 ms

# ping 192.168.0.254
PING 192.168.0.254 (192.168.0.254) 56(84) bytes of data.
ping: sendmsg: Operation not permitted

#ping google.com
ping: unknown host google.com

# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 eth1
0.0.0.0 192.168.0.1 0.0.0.0 UG 0 0 0 eth1