BUG #1420: Doesn't accomplish connection with the server

The following bug has been logged online:

Bug reference: 1420
Logged by: Byron Zambrano
Email address: bfzambrano(at)yahoo(dot)com(dot)mx
PostgreSQL version: 8.0.0 - rc5
Operating system: Win Xp Service Pack 1, 2
Description: Doesn't accomplish connection with the server
Details:

I like programming and I use PostgreSQL 8.0.0 for Windows. The operating
system from my computer is Win Xp.

PostgreSQL works perfectly if the Win Xp does not have installed Service
Pack, the problem occurs when Win Xp has Service Pack 1 or 2. PostgreSQL
does not activate or doesnt work and it presents this error:

PgAdmin III

An error has ocurred

Could not connect to server: no route to host(0x00002751/10065) Is the
server running on host "192.168.0.1" and accepting TCP/IP connections on
port 5432?

I would like to know why it happens

Thanks for your collaboration and I expect your answer.