Ubuntu Networking :: No DHCP Offers Received After Modem Change?

I used to connect to the internet via a Linksys router using the following terminal commands (Network Manager has never worked for me on any Ubuntu install):

Code:

sudo ifconfig wlan0 down
sudo dhclient -r wlan0
sudo ifconfig wlan0 up

[code]....

However, I recently changed the old modem + router for a new wireless modem (a Thomson TG585v8 ). Now, the result of that last command is this:

Code:

amosupremo@amosupremo:~$ sudo dhclient wlan0
Internet Systems Consortium DHCP Client V3.1.3

[code]....

No working leases in persistent database-sleeping. I've tried to connect in Natty(both Ubuntu and Kubuntu) and it's not working either.I also purged Network Manager and installed wicd and I managed to get an intermittent, slow connection.

1 ) Machine Brand and Model (PC/Laptop): No brand. I built it with the following specs:

AMD Athlon II X4 2.6GHz
2 HD: 100GB Sata (Ubuntu and XP64 install) / 80GB IDE (XP)
4GB RAM
Gigabyte Motherboard

2 ) Wireless Brand, Model and Wireless Chipset:

Code:

amosupremo@amosupremo:~$ lsusb
Bus 002 Device 005: ID 0ace:1201 ZyDAS 802.11b
Bus 002 Device 004: ID 049f:000e Compaq Computer Corp. Internet Keyboard

[code]....

3 ) check interface:

Code:

amosupremo@amosupremo:~$ ifconfig wlan0
wlan0 Link encap:Ethernet HWaddr 00:02:72:04:d0:04

[code]...

I am also attaching the wicd log. It contains a session where I got the intermittent connection. I stopped that connection and restarted it (with the same results) two times.