"Log: 'System' Date/Time: 27/02/2011 12:53:38 PM
Type: error Category: 0
Event: 1000 Source: Dhcp
Your computer has lost the lease to its IP address 192.168.100.10 on the Network Card with network address 0013D492876E.
Log: 'System' Date/Time: 27/02/2011 12:53:06 PM
Type: error Category: 0
Event: 1002 Source: Dhcp
The IP address lease 192.168.0.2 for the Network Card with network address 0013D492876E has been denied by the DHCP server 0.0.0.0 (The DHCP Server sent a DHCPNACK message)."
Or is it jumping between your router and your neighbor's? Or were you playing with the router at this time?
The error with SP3 has a MS fixit on this page:
http://support.microsoft.com/kb/949377
Try it and see if that helps.
Ron