Damn...that sucks Evil. Dillinger is one of the best hardcore groups around. I live in Norcal, and watched those guys as they were comin' up.
My thoughts:
Definitely could have been mic-in, but that would likely not be the clicks and pops. Here's a funky-nut for you. The heat-wave is sportin' some major rank over the atmosphere. Were you in a humid area? It is possible that an excessive amount of humidity on the jack made your connection (in the jack itself) less than stellar. When I lived near the coast, I had that happen a few times during beach sets. The combination of heat and electrostatic winds fucked up more than one tape with those exact cracks and pops.
With digital recording, I thought the cracks and pops came from the connection (i.e. the jack or the cable not being meshed).