There are two different NI-IMAQ drivers: one for the IEEE-1394 interface, and one for the PXI/PXI frame grabbers. LoadInterfaceDefaults is an NI-IMAQ command and is not supported by the NI-IMAQ 1394 driver. The method is looking for a valid version of NI-IMAQ (2.x), which will not work with 1394 cameras.
The 6.0.4 version is actually your version of NI Vision, which is the image processing toolkit for IMAQ.