This sounds like a job for PingPlotter. Start PingPlotter tracing to a game server that you regularly play on. Use a 2.5 second trace interval. Run PingPlotter for a few hours during a period where you also try to play your game - and you have problems. If the problem is chronic - just so bad you can't really play at all, then just collect data. If, though, it happens sporadically, then make note of the problems by right-clicking the time graph in PingPlotter and enter comments at the period where you had problems.

After you've collected a few hours of data, save off the data (File -> Save Sample Set...), then email that to support@pingplotter.com. We'll have a look at it and see if we have any advice for you. We can also post a picture back here with the data we think is pertinent.

- Pete