hi, does not sound quite the same as what i had a few years ago. to fix it all i did was identify the srs ecu part number - having removed the parts needed to access it, then i bought a matching part number off ebay. changed it over, and it worked straight away and has been ok since. There are different part numbers for those cars with pass and driver airbags or just a drivers one.
i think you will also have to see what philip says about what pscan is doing..