The thing is, Sp2 may fix the problem that you are having.. but then again it may make matters worse...

You can try the msconfig diagnostic startup, and if you get the problem with the diagnostic, then you can pretty much rule out any software on startup causing the afd.sys issue.. no matter how random it may seem.

The reason I pointed out zonealarm or a firewall is because afd.sys handles tcp/ip communications amongst other functions. The firewall could be preventing afd.sys from loading..

One other check would be to uninstall your NIC and reinstall it in the device manager. That or disconnect the cable from the internet and see if you are getting this problem.

Could be a conflict with your NIC and afd.sys.. could be a lot of stuff.