I am trying to speed up the time it takes to open large assemblies.  I always use large assembly mode (my default setting for large assembly mode is anything over 20 parts) and prefer if everything loads in lightweight.  However, I can't figure out why specific parts and subassemblies of top level assemblies refuse to open in lightweight.  I can right click on the top level assembly and say set resolved to lightweight but some assemblies/parts refuse to open in lightweight to start.  Also, some subassemblies and parts refuse to ever go into lightweight even if I click on them and say set to lightweight.  What is the cause for this?

Thanks, John

SW2011x64  SP3

Windows 7 x64 Professional

Dell Precision T5500

Dual Quad Core Xeon x5677 @ 3.47 GHZ

12 GB RAM