Help please. Problem with yarn

[Cherami]

I am trying to cast on Modadea Tweedle Dee yarn that my DD picked for a hat. And when I twist it while casting on, it unrevels. To the point that it breaks and pulls apart. Its fine when i knit it, but casting on is a real problem. Any ideas how to keep it from happening?
Thanks

[felted-bag]

Are you using a long tail cast on? If so, try a knitted cast on.