Helo.
I have a problem. If I'm trying to simulate a dforce outfit. This happens many times, but not always! Has anybody ever seen something like this?
One of the most common causes of this is self-intersection. In other words, due to the pose the character is in, parts of the clothing mesh are passing through other parts. This will tend to cause dForce to freak out, the simulation to get unstable and POOF - a new art form instead of simulated clothing.
The most straightforward way to get around that is to start the character in the A-pose (for G8) or T-pose (for G3) and then allow the character to gradually move to the desired pose. This gives the cloth time to get out of its own way over the course of the simulation. If you run the simulation with the "Start character from memorized pose", as opposed to from the current pose, it might fix the problem.
If that doesn't work, then perhaps you need to adjust the pose so it's somewhat less extreme, simulate that, and then tweak the pose into its final position afterwards. Basically, look for places where arms might be passing through the clothing, or the armpits are too "tight," etc.