Many thumbnails seem to be missing, any idea of the cause?
Some firewall programs, in particular Norton Internet Security, block images that are the same size as some common advertisements. Unfortunately many thumbnails and some map images happen to be this exact size. So if you use such a program you might like to try turning it off temporarily and trying again, and if that gets our images back, then have a look for the option to disable this, arguably, flawed method of security.