Ive just discovered that when the error occurs and it is first put into the pc it then shows as there is no more room on the card (h2testw also confirmed this), but then having put the card back into the phone where it showed up as normal, allowed me to take pics etc and access it, and then back into the pc, it also showed as normal with 40gb spare and h2testw was able to scan the card.(ongoing now)
whether this is a phone problem or a sd problem I do not know, my phone did update i while i was in the process of it having disappeared maybe that is a fix i dint know.
thanks john..