Guys, I think whats happening is that sometimes when we create blocks from entities on other layers and layer '0' is turned off this will cause the selection/block to then disappear from the main cad window.
I've tested this several times now and its always the case and also you will get a warning in the command line that states:
' Trying to draw on or modify entities on a locked or invisible layer
Maybe this is our ' phenomenon'
Have a test too and let us know if this is the case?EDIT:
Actually this will happen 'every time' if the layer we are working on at the time of creating a block is turned off!
Hope this makes sense.