Some notes (after a few experiments)...

1. Parenting is not the answer. The same thing happens - the cloth falls off the cylinder. Also, if the cloth-plane is parented to a distorted (ie, made long and thin) cylinder, the cloth-plane also gets stretched (in the same dimensions, where applicable) as soon as parented. Not wanted...

2. The same thing (the constrained cloth falling off) also happens if the long, thin cylinder is exported/imported as a new prop. Whether parented or not. This is true in both P5 & P6.

3. I also tried starting with the cylinder near the ground and moving it up during the simulation. Similar effect, the cloth, even tho constrained, still falls off...

4. And I tried using a second, large square, just above the ground, to replace the ground (just in case there was a "feature" asssociated with the ground.....but the cloth still fell off.

Where to go from here???

Some ideas (which I don't have time to try out tonight)..

• Maybe Poser is getting confused as to which object to constrain to. Perhaps exporting/importing both the cylinder & the ground (or a square), thus creating a single prop of them both will help Poser resolve its confusion (if that's what the problem is)...
• Convert the cylinder into a figure (no rigging needed, so shouldn't be too difficult)...

Sorry I couldn't help further:-(( .. but maybe what I've posted will help other avoid dead-ends..

Cheers,
Diolma