For the benefit of future searches............................
I had this problem looked at by Bunbury Subaru
the car was throwing a code 11 - after testing the function of various airbag system components the trouble was narrowed down to the airbag module or the roll connector - these components where removed tested and found to be ok - after reinstalling them the code cleared - so it seemed to be a poor connection that just required re-plugging - cost $50