I loaded in an existing pcb layout and updated a component from the library panel on the right side. This action seems to have locked up the pcb layout. i.e. nothing is now selectable. I closed the layout and CS and reopened both and the pcb layout is still not selectable. I opened another layout and it is selectable so it seems that the first layout has been corrupted. Do you know of any operation that can re-open the pcb to editing?