I had the same problems as you. I contacted them, and it didn't help in the slightest.
Solution: Drop doubleTwist and go use the HTC Media Player. It is by far one of the best media players on the market(not technically on the market) or use the Cyanogen mod one. I am currently very happy with the Cyanogen mod media player, and I've found that there are many features doubleTwist is lacking(most being the same issues that the iPod app on the iOS has), that most other players do. I used doubleTwist for a while, it was great, the UI was great looking, it was fast, but it didn't do many things I wanted. First off was the lack of playlist editing. If I download an mp3 straight to my device, I want it on my playlist. This is where it fails the most for me. I also tried a very iOS like media app, but I left it because of it's downfalls, (being the iOS like UI). If you're worried about lockscreen controls, Android has it just as good as iOS. We've got this niftly little app called "WidgetLocker" that allows us to put widgets on our lock screens. That means more than just music controls (although right now I have only my media player widget, Pandora Widget, and Beautiful Widget small on it). So, drop doubleTwist. Get widgetlocker and your favorite media player other than doubletwist.