Thumbs and tools gone ?!?

OK,

For some weeks now, some strange C1 5.1 behaviours.
When editing pics, sometimes the thumb dissapear and I cannot see the properties on the Tools anymoe.
Really don't know how this can happen.

Here a print screen.. maybe someone has an idea why

http://farm5.static.flickr.com/4051/4447848434_ce5526f43d.jpg