Hmmmm... Interesting problem. I've been trying to replicate it without any luck. Turning on and off 'Soft Shadows' for the 'Sun' doesn't give me any trouble, nor does turning on and off and changing the settings for 'Total Internal Reflection'. In each instance a bottle with the Standard Glass material renders properly for me. Is there anything else in your scene besides what is seen in the render? Anything at all besides the two radial lights and the camera? Did you double check the glass material or try a different glass material? Seems to me that I had a similar problem to this once and the only way I could get around it was to bring all my separately saved objects into a new file and resent the camera and lights. But I could be remembering that wrong. The ideas that 'Soft Shadows' or 'Total Internal Reflection' settings could be causing the rendering error sounds plausable, but I somehow have trouble believing that either would be the only cause... however, I really don't know. It certainly isn't caustics. I'm look foward to hearing what you find with regard to the cause and solution to this problem. Hope you solve it.