Hey folks can anyone solve my latest mystery for me? I use Poser 5 and when I go into the cloth room to create a cloth simulation, I run into a strage problem.
I'm using Posette and having her sitting on a large stone, and I'm trying to have a nice summer dress draped across her. When I'm setting up the simulation, and I click "collide against", if I put a check mark by Posette that's fine, but if I put a check by the stone she's sitting on as well, the simulation won't run. 
So to see what would happen, I put a check next to Posette, but not the stone, and ran the simulation. Now, the dress is draped across her lovely legs, but it protrudes into the stone she's sitting on, instead of draping across that as well. Needless to say, this simulation is useless to me. I tried to check her and the stone again, and the simulation stalls before it ever even begins.
Has anyone else run across a similar problem, and if so what did you do to solve it? I need to drape the dress on her. Due to her pose, a dress from my "conforming clothing" set just doesn't work.
Help!
Thanks

The cloth simulation can stall if the cloth gets "trapped" between two surfaces. Try setting up your simulation so that the stone moves into position gradually during the course of the calculation; even if it stalls, you should be able to use the last frame which worked.

I've made figures sit on chairs before and haven't had an issue.  Maybe it's how you are setting up your simulation?

Here is what I do:

In Pose Room....

1.  Add figure
2.  Add dress
3.  Add chair

1. Go to frame 15 (of 30 frames)  and add your figure's pose so that she's sitting in the chair
2. Go back to frame 1
3. Move to cloth room

In Cloth Room...

1.  Create new simulation

• 20 frames
• Cloth self collision

2.  Clothify the dress

• pick your figure
• pick whatever else the dress will come into contact with IE: Stone, ground
• If not into contact with head, hands or feet, check the appropriate boxes. if those parts are involved, leave them unchecked.

1. Save your file

4.  Run simulation

As Bob says, Poser will sit there forever if your simulation starting positions have the cloth intersecting any portion of the figures or props that they're supposed to collide against. Since your current setup stalls when you add the rock. It's pretty certain that the cloth is intersecting the rock somewhere in it's current starting position. Lower the rock in frame 1 of the simulation to a position where it doesn't touch the cloth and then place it in it's final position in frame 30. This will make the rock come up to meet the cloth as the cloth comes down to drape upon it..

Another tip: turn down collision offset and collision depth to 0.2 or 0.3.