A lot of the time issues involving seemingly 'blank' cartomizers or different tastes are down to the battery. Over time the amount of power a battery can deliver will diminish. A dying battery will not be able to vapourize the liquid to the same level it did previously which may cause the odd taste you are experiencing. Due to minor differences between coils in cartridges, the battery may not be able to fire the cartomizer at all. It is recommended to change your batteries every 2-3 months so if yours is older than this it may be time to purchase a new one.