I'm having a similar problem. I know very little about networking, but I'm learning. Right now I'm just trying to get the connection working again so I can continue a course I'm taking. I am using a vm machine - and was able to connect fine until I created another vm of Janus. Somehow it messed up my connection because now I can't connect. It's not a wireless issue as I am plugged in with a cable.

When I type /etc/init.d/networking start this is the output:

[SPECIAL]Reconfiguring network interfaces...Internet Systems Consortium DHCP Client V3.1.1
Copyright 2004-2008 Internet Systems Consortium.
All rights reserved.
For info, please visit DHCP | Internet Systems Consortium

Listening on LPF/eth0/00:0c:29:57:c6:2c
Sending on LPF/eth0/00:0c:29:57:c6:2c
Sending on Socket/fallback
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 8
DHCPOFFER of 192.168.239.128 from 192.168.239.254
DHCPREQUEST of 192.168.239.128 on eth0 to 255.255.255.255 port 67
DHCPACK of 192.168.239.128 from 192.168.239.254
bound to 192.168.239.128 -- renewal in 716 seconds.
if-up.d/mountnfs[eth0]: waiting for interface eth1 before doing NFS mounts
if-up.d/mountnfs[eth0]: waiting for interface eth2 before doing NFS mounts
if-up.d/mountnfs[eth0]: waiting for interface ath0 before doing NFS mounts
if-up.d/mountnfs[eth0]: waiting for interface wlan0 before doing NFS mounts
eth1: ERROR while getting interface flags: No such device
Internet Systems Consortium DHCP Client V3.1.1
Copyright 2004-2008 Internet Systems Consortium.
All rights reserved.
For info, please visit DHCP | Internet Systems Consortium

SIOCSIFADDR: No such device
eth1: ERROR while getting interface flags: No such device
eth1: ERROR while getting interface flags: No such device
Bind socket to interface: No such device
Failed to bring up eth1.
eth2: ERROR while getting interface flags: No such device
Internet Systems Consortium DHCP Client V3.1.1
Copyright 2004-2008 Internet Systems Consortium.
All rights reserved.
For info, please visit DHCP | Internet Systems Consortium

SIOCSIFADDR: No such device
eth2: ERROR while getting interface flags: No such device
eth2: ERROR while getting interface flags: No such device
Bind socket to interface: No such device
Failed to bring up eth2.
ath0: ERROR while getting interface flags: No such device
Internet Systems Consortium DHCP Client V3.1.1
Copyright 2004-2008 Internet Systems Consortium.
All rights reserved.
For info, please visit DHCP | Internet Systems Consortium

SIOCSIFADDR: No such device
ath0: ERROR while getting interface flags: No such device
ath0: ERROR while getting interface flags: No such device
Bind socket to interface: No such device
Failed to bring up ath0.
wlan0: ERROR while getting interface flags: No such device
Internet Systems Consortium DHCP Client V3.1.1
Copyright 2004-2008 Internet Systems Consortium.
All rights reserved.
For info, please visit DHCP | Internet Systems Consortium

SIOCSIFADDR: No such device
wlan0: ERROR while getting interface flags: No such device
wlan0: ERROR while getting interface flags: No such device
Bind socket to interface: No such device
Failed to bring up wlan0.
done.[/SPECIAL]

When I do an ifconfig -a I get:

[SPECIAL]eth0 Link encap:Ethernet HWaddr 00:0c:29:57:c6:2c
inet addr:192.168.239.128 Bcast:192.168.239.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fe57:c62c/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:75 errors:0 dropped:0 overruns:0 frame:0
TX packets:196 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:12592 (12.5 KB) TX bytes:16664 (16.6 KB)
Interrupt:19 Base address:0x2000

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:37 errors:0 dropped:0 overruns:0 frame:0
TX packets:37 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:3573 (3.5 KB) TX bytes:3573 (3.5 KB)[/SPECIAL]

I had it working before, and as I mentioned, I know little about networking - any help would be greatly appreciated.