Hy rustednuts, all I can think of is a weak spark, if it was running then the timing couldn't have been that far out. We had a case a week or two ago where there was a poor ground at the distributer point mounting plate, resulting in no spark. You say you have spark in the air, but is it enough to fire plugs under compression, what colour is the spark, if it's not blue it's not very strong, hope that helps.
