Based on the clone pic in your sig thread:
Trim the tip half off the leaves while you're taking the clones.
As I understand it, the stem can't uptake enough water from the soil to keep up with the transpiration from the intact leaves - the drooping means the plant is drying out. Once the roots start to form and can suck up water they'll perk up. Since I started doing this, I haven't had any drooping clones.
I've got some kind of 'mystery infection' I'm trying to figure out...but no drooping.
Trimming the leaves reduces the surface area that's transpiring (how a plant breathes) to a point where the stub can keep up with the moisture loss. There's also only half the weight hanging on the stem that way.
An added benefit is that you can monitor new growth more easily: any leaves with a tip are new ones.
If an air bubble has gotten into the stem, they may be done for.