See if all your levels are turned on. If there is an object in a level that is turned off, the screen will still zoom as if it is there.
Another thing to watch for when importing CAD files is if entities are converted to GROUPS,
they can be UNGROUPED with the EDIT option ( CTRL+E ). This sometimes gives problems when viewing all objects ( CTRL+A )
If there is some kind of invisible object causing the problem you can select and copy the good objects to the clipboard then open a new drawing and paste them back in to remove any bad objects.
Another thing to watch for is having a WHITE objects on a WHITE screen. Use the SELECT OBJECTS to find these objects, you may have to ZOOM OUT a little.
Another thing to watch for when importing CAD files is if entities are converted to GROUPS,
they can be UNGROUPED with the EDIT option ( CTRL+E ). This sometimes gives problems when viewing all objects ( CTRL+A )
If there is some kind of invisible object causing the problem you can select and copy the good objects to the clipboard then open a new drawing and paste them back in to remove any bad objects.
Another thing to watch for is having a WHITE objects on a WHITE screen. Use the SELECT OBJECTS to find these objects, you may have to ZOOM OUT a little.