Thanks, J. Just what I needed: the confidence to go jabbing something sharp into the SD card slot
You're right though, and it's what I would have expected: there is a final "click", after which the card is held right within the slot, without the cover being required to do any holding down. It didn't seem right before.
However, the design ain't great, because anyone having fingers larger than a small child will really struggle to push the card deep enough into the tiny slot for it to engage properly. I did try several times using my finger, to get it as deep as possible, but it didn't click in. In the end I used the end of a pen, but with a wide elastic band in between the pen and the card/slot to ensure the pen didn't slip past the card and damage anything.
Having the card half-engaged like I did originally, it is not surprising that I corrupted the card -- must have disconnected as the BB was trying to write folders to it the first time round. At least the disk checker on Vista was sufficient to fix it.
Thanks very much.