Safari activity window reports 'About:Blank'

In Safari 3 and 4 the activity window shows a directory entitled 'About:Blank' which expands to show an entry called 'About:Blank'. I believe that this indicates that some javascript has failed to load. The message is being generated because of Lightbox2 module. I've disabled all contributed modules other than Lightbox2 and Jquery Update and the message still appears. Removing Lightbox2 module prevents the message appearing.

When I view the demo page through Safari : http://stellapower.net/lightbox2 the message does not show up - but perhaps the demo uses 6.x branch?

This is not exactly a bug as my images are displayed as I would expect - but I would like to know why this message is being displayed - and try to fix whatever safari doesn't like.