Some help with dielectric node

Hi,

I just started using node based surfacing (which I find really
amazing).
I made simple sphere and choose a dielectric material node.

The result is that the sphere looks really black (evil looking
black:).
It does not really seem transparent (I put the absoption factor to 5)


I use ImageWorld to in my scene and 2 area lights (set a 60 and 40%)

I would expect to see a nicely rendered glass sphere in stead of the
black sphere from hell.

any ideas what I am doing wrong

With kind regards,

Kris