I'm having the same problem with mine, but using the bigger cylinder shaped atty with 2ml tank. I just installed a fresh new atty and tank, and it will taste good for a while, then go to a burnt taste until I pull the tank, pop it back in, and kinda get it re-primed I guess.
Not sure if the atty just isn't getting a good flow of juice, and how to fix that if that is the case.
your on about the ego c right?
Its a wicking issue that's been on going for some time now,search around the forum,there arn't really any quick fixes,you may find you want to use stainless steel wicks,i just leave mine a couple of hours and when i go back to it it seems find for a while them goes again.
I now use a different cartomiser.