I'm not sure if my advice will help or not, but I hope it will.
Are you using DHCP or a Static IP address? If you're using DHCP, make sure you're assigned an IP address:
sidoh@tehserver:~$ /sbin/ifconfig
eth0 Link encap:Ethernet HWaddr 00:40:CA:3A:7E:C4
inet addr:10.0.0.15 Bcast:10.0.0.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:114926743 errors:0 dropped:0 overruns:0 frame:0
TX packets:152516208 errors:0 dropped:0 overruns:16 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1114152487 (1062.5 Mb) TX bytes:3104831718 (2960.9 Mb)
Interrupt:10
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:5311 errors:0 dropped:0 overruns:0 frame:0
TX packets:5311 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:274289 (267.8 Kb) TX bytes:274289 (267.8 Kb)
If you're not assigned an IP address, try assigning yourself one by editing /etc/rc.d/rc.inet1.conf
sidoh@tehserver:~$ vi /etc/rc.d/rc.inet1.conf
When you're doing this, make sure you set your DNS and Gateway to the IP address of your router. Also, make sure to follow the patterns for IP addresses that you get from your windows box by running ipconfig /all. Keep the same subnet mask too.
# /etc/rc.d/rc.inet1.conf
#
# This file contains the configuration settings for network interfaces.
# If USE_DHCP[interface] is set to "yes", this overrides any other settings.
# If you don't have an interface, leave the settings null ("").
# Config information for eth0:
IPADDR[0]="10.0.0.15"
NETMASK[0]="255.255.255.0"
USE_DHCP[0]=""
DHCP_HOSTNAME[0]=""
# Config information for eth1:
IPADDR[1]=""
NETMASK[1]=""
USE_DHCP[1]=""
DHCP_HOSTNAME[1]=""
# Config information for eth2:
IPADDR[2]=""
NETMASK[2]=""
USE_DHCP[2]=""
DHCP_HOSTNAME[2]=""
# Config information for eth3:
IPADDR[3]=""
NETMASK[3]=""
USE_DHCP[3]=""
DHCP_HOSTNAME[3]=""
# Default gateway IP address:
GATEWAY="10.0.0.2"
# Change this to "yes" for debugging output to stdout. Unfortunately,
# /sbin/hotplug seems to disable stdout so you'll only see debugging output
# when rc.inet1 is called directly.
DEBUG_ETH_UP="no"