When I open Solidworks 2016 on a item that has several sub assemblies the BOM does not show up. I can hide it then show it in the tree and it will show up, However I can not double click to edit. Solidworks treats it like as snapshot instead of an active table. If I go to a part and change the properties at the part level,  the changes will show up in the assembly only after I close the assembly and reopen, hide the table, then show the table. However the table is still not editable. This only happens once I have 40 or more items in the BOM. Restarting Solidworks and restarting the PC makes no difference. Deleting some of the parts from the drawing will make it work as expected.

In this particular case the BOM has 635 Parts and 65 Lines ( 65 Unique Parts). The number of parts is not the issue so much as the number of lines (or the Number of unique parts) 40 is a rough estimate. but is about where I start seeing the issue.