I have an NX assembly that consists of metric and english parts in a metric assembly template. I have added this assembly to a metric Master Model Drawing and created a parts list. However, only the metric parts are showing up in the list, none of the english/inch (sheet metal) parts are showing up and nothing I try seems to be working.
I had to test this just to be sure but it should work without any hiccups.
Things to check:
1) Use Edit Levels to check that the metric components highlight in the Part Navigator.
2) Check the that attributes REFERENCE_COMPONENT, PLIST_IGNORE_SUBASSEMBLY or PLIST_IGNORE_MEMBER have not been assigned to the components not listed.
3) Did you use a Parts List Template? If you did, try the default parts list to see if everything is listed.