I have a couple of lights, not directly behind the balloons but I have a back light there...
I don't know too much about sss but I thought it would be the right approach.

banksta: That trick didn't work... ended up creating the strings from polys. This time I applied a texture with varying transparency ans specular color. Still needs refinement though.

Here's a rough sketch:

Lots to do yet...

I found out the problem with saving the file is actually caused because the sss shader has 0 alpha for some reason
Can someone post a tutorial on sss? Google turned up with lots of pretty much useless stuff . I remember seeing one in highend3d but it seems to be down right now.

Thanks in advance,
Benny