A little update on my problem.
So I played around a bit, cleaned the battery repeatedly, pulled the pin up some more (up to 10mm), stuck the clearo on, still nothing. Resistance was NON, didn't fire. Other clearomizers still working fine...
So I bit the bullet and cleaned out the tank and took it apart. I took of the coil and just attached the base. Bridged the connection with a wire and tested the resistance, which came up as something like 0.2ohm. So the base connection is fine. I reattached the coil and sure enough the resistance measurement came up NON, signifying a break in the circuit in the coil.
I played around with the coil some more and tried screwing the coil on really tight. Eventually I got a resistance measurement. Something like 3.6ohm although it's a 2.0ohm coil, but it was something.
So I put it back together, stuck in some cheap juice and tried it out. It's working again. Eventually it stopped working and then I finally noticed the actual problem; the coil was bent a little. I think this was causing a problem with the connection between the coil and the base. So I played around with it and straitened it up and that got it working again. It's been working since.
I also solved the issue with the resistance measuring high sometimes. I have some CE4s which seem to be cheap clones. They seem to be pushing the pin down slightly further than is comfortable for the iclear16s. If I pull the pin up the iclear reistance measures properly even if I interchange them. As soon as I put a CE4 on I have to adjust that battery pin again.