Based on the information you've shared here, I can't really say what the problem is.

PingPlotter isn't really showing any network problems (no packet loss, and no clear latency spikes). This would indicate that your problem isn't going to be highlighted by ICMP troubleshooting (which also indicates that it's not a *network* problem).

This could be a firewall problem (since you can't connect to games at all), but I'm not really sure. Do you have another computer available to eliminate that it's a problem with your computer?