I've had two ignition problems in my short time running gas engines for R/C. My first problem last season was identical to DMcQuinn's second problem, though in my case it was due to the threaded on tip on the top of a new NGK not being tightened properly, I know now that they have to be tightened out of the box[:-] .
More recently, I had gotten my Yak 54 ready for the season and ran it up at home, no problem. When I got it out to the field it would want to start, but would die within the first second of starting at idle. Bottom line the cheapy XYZ (blue plastic module) was toast. I replaced it with a new RCExcell and also bought the RCExcell ignition tester that drives the ignition module without running the engine. It seems like a must have when troubleshooting an ignition problem[8D]
Pete