I point people there because some people are too lazy to look for their answers.

Something to try is under your Tools -> Options -> Searching, disable OOB.

The problem 'might' be unreliable UPnP implementation within your router. In that case it's worth trying forwarding a port.

If you are willing to try manual port forwarding;
Step 1: Static ip for Windows XP (this MUST be done before step 2)

Step 2: Port Forwarding for the ZyXEL P-320W

BTW you don't necessarily need to choose port 6346, you could try any between 49152 - 65535, which are less likely to be affected by ISP interference. Example 64049 or 50651.

You may need to reboot your router to get the new instructions into operation, depends on brand & model. Likewise, it might be wise to reboot your computer to freshen your router's reading of ip number.