Seen this a few times now, pretty weird new issue.
Some managed to pull the card out - and after that it worked fine, so it seems like the spring is stuck somehow and is fixed by removing the card.
Actually I think the slot is too tight (or better: exact to specs). I had to open my pandora 2 times to gently push the sd-card out of the slot.
This was with a micro-sd->mini-sd->sd-card slot converter, and with a genuine TomTom for WinCE sd-card. (to be clear: The ipaq runs linux! I just got it from someone else).
That TomTom card probably had a label that made it too thick. This TomTom card would work perfectly in my SmartQ 5, but then again, the spring in the SmartQ 5 is too strong, so you would be able to break the sd-card pushing it in.
Most of my SD-cards just work perfectly, so the first time I use another sd-card, I just push it in very gently to look if it would get stuck.
The plusside of opening the pandora was that it forced me to loosen the screw near the usb port, which was probably too tight because a crack was appearing. (Next to the fact that the original screwdriver was probably a bit to big to put in the pandora holes ;-) ).