Seems to still be a problem with 64-bit instances. At least for me if I use the high-bit it will fail to load the object throwing an exception:
line 303, in _load_definition
KeyError: "resource does not exist: '00000000!8dbb6d4e'f7429c80.c0db5ae7'"
If I changed the instance ID to 0x0DBB6D4EF7429C80 it loaded up without issue.
ETA: To clarify, the COBJ appears to load (object appears with red X in build/buy) but the OBJD fails to load.
ETA 2.0: Pbox got me straightened out, it appears that using 0x80000000 for the group will restore sanity.
