A case of disappearing parts

I'm working on a large assembly (5,000+ parts), and I wasadding a new config. when suddenly more than half my parts arehidden. There are sub-assemblies within sub-assemblies withinsub-assemblies...etc. I am having to go through and unhide a ton ofstuff. Does anyone else have this problem? I have had this happenwith another assembly in the past, but it wasn't near as large asthis one. But it was the same thing, I would be doing somethingwith configs and it would all of a sudden hide over half the parts.

I have SW 2008 SP5.0, Windows XP 64bit. I am working in LargeAssembly Mode, but I did not choose the option to Quick view /Selective open, nor did I check the Do not load hidden componentsbox. Thanks to anyone who can help.SolidworksAssemblies