That is the same as mine - out of interest what sound card are you using. I am using an Xfi Extremegamer sound card. Supreme Commander apparently had this issue as well

I've had the same issue as Aryanna and Tals, that is to say, it's been completely remedied by removing audio (except for the lack of audio x.x )

Concerning the AI calls, I would agree that something's a bit off with the overall efficiency of the code based on what I've heard, and I have a few friends who all say that the game runs better in multiplayer. Like Aryanna, multiplayer is something I've been avoiding (except for a few lan games with aforementioned friends, since their simspeed is usually no better than mine ) at least until I get things running smoothly WITH sound.

I will say that using zoom has helped a little when I was really lagging with the audio, but I think that may be more wishful thinking on my part than actual results, since the framerate never stayed up for long.

Good luck, to everyone =P

Sadly, this problem happens to me too and I cannot find a way to fix it!  I've tried setting settings down to lowest, but it still gets the 10 second fits of super lag/fuzzy sound.  My system is fairly good, can run this game at highest with ease and runs far more demanding games.

Vista

Intel Core 2 Duo @ 2.5Ghz each

Nvidia GEForce 8800GTM 256mb

4 GB RAM

I am glad I'm not the only one with this problem, but a fix really is needed.  Havn't dared to try multiplayer yet, due to the reportedly poor servers and this problem.