Welcome bongraider,
Yes, glass panes must have depth. All objects with specular or glossy trnasparent materials should be closed volumes, so light may enter
and exit the transparent medium. This way the result will be different.
Also, I don't think that Whaat has released already SkIndigo for 2.6.1, but this last Indigo version has an option to speed your render up.
see Ono's "How To" on Glass Acceleration here:
http://www.indigorenderer.com/forum/vie ... 14#p101214