Turn off Zonealarm if you have it, it's been found to cause lag problems. I used to have these severe multisecond lags a lot, and it was really annoying, but turning off Zonealarm helped a lot. I have since switched to kerio personal firewall and it works great with cs source. If that's not it, you might be suffering a lot of packet loss on your connection, although it would be pretty extreme to cause really severe lag spikes like that. Hope that helps!