Wireless connection HELP

Hello,
Briefly: A couple of days ago wireless connection stopped working in my PC (XP Media Center, SP3) while my laptop (Vista) connects to the same network without any problem.

Using Realtek RTL 8187 USB adapter for my PC's wireless connection - used to work OK for last 3 months until 4 days ago.

It takes a while to acquire network address but then after acquiring the address the PC receives no/little pockets.

Some other details:

ipconfig /all

Ethernet adapter Wireless Network Connection 17:

Connection-specific DNS Suffix . : hsd1.nj.comcast.net.
Description . . . . . . . . . . . : Realtek RTL8187 Wireless 802.11g 54M bps USB 2.0 Network Adapter #2

Dhcp Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 192.168.15.101
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.15.1
DHCP Server . . . . . . . . . . . : 192.168.15.1
DNS Servers . . . . . . . . . . . : 68.87.64.146
68.87.75.194
68.87.71.226
Lease Obtained. . . . . . . . . . : Tuesday, June 09, 2009 9:11:18 PM
Lease Expires . . . . . . . . . . : Wednesday, June 10, 2009 9:11:18 PM

TCP/IP proprties : Obtain IP address automatically.

a) windows firewall off
b) anti virus ( webroot ) shutdown/ disabled

Router Dlink 524.

any help will be appreciated.

Thanks