Using a Parafin, and having the same trouble. Haven't had this happen for quite a few years....im thinking it has something to do with the additives in the wax. Because I too have used the same wax,wicks,scent etc. through the years and then Bam...I'm having problems. New case of wax though. First slab seems to be burning fine, the second slab is messed up. At $100 a case....makes me sick.