is it a prop or a conforming figure?

 

If its conforming make sure not to conform it. I find this causes alot of oddities. If you need to start the draping from a specific pose, pose the character with the pants conforming, and then export the pants to and OBJ file. re-import unticking every option and the pants will pop right back into the correct place for you. then drape that object.

 

Also, if the object has morph dials that you are using (ie not 0) then this can cause funkiness unless you ZERO all morphs in frame 2 (assuming you are starting at frame 1).
At the start of the dynamics calculation it takes a "snapshot" of the model, which includes morphs. but once the calculation is complete, Poser will then apply the morphs to the draped cloth, depending on how it draped, this can make things go haywire (or just crash poser)

 

If your having problems getting them to fit properly, use the figure morphs to make him thinner than you want at frame 1. then at say frame 5, reset the morphs and beef him up again.  I use this ALL THE TIME with V4 to make sure things fit properly no matter which female figure they are for.

TemplarGFX
3D Hobbyist since 1996
I use poser native units

167 Car Materials for Poser