@ Dragon: I have the same problem, also using Capping but I don't think Quartz has (or should have) anything to do with it.
And I have a request, I always thought it would be cool to see instant casts (on global cooldown) in your cast bar. While Pitbull castbars lacks a lot of things, it is capable of displaying instant casts.
Currently I'm using those 2 bars on top of eachother, but its not really ideal:
I'd like to see an option for instant cast display included in a new quartz version. And if you consider it possible and worth it, including the appropriate spellicon (something Pitbull doesn't have for its instants) would make this addon even more outstanding anjd awesome!