Why are my internet book marks 'white'?

[Ashington]

Very strange. When I'm viewing the internet and have several web pages open at anyone time when i press the 'window' button to view them they are displaying in white i.e. not showing the actual webpage.

This seems to happen more so on forum sites for some reason.

Anyone else noticed this?

 

[nx1977]

Yes, they update on every visit. If interupted then they dont download the thumbnail.