If you leave the virtual memory extension "on" then you have occupied your card, it can't be exported. Those 'swapoff' suggestions in other posts are workarounds trying to turn off the vm extension feature behind its back, so to speak.

BTW, I've started using the vm ext. feature, and the 'enhances performance' meme is nothing but an urban myth. It does not enhance performance (and it was never explained why it should, when it doesn't on a desktop computer). Instead, it does exactly what it's for: It is an overflow catch, i.e. it keeps the device (or rather, programs) from crashing due to using too much memory. If you monitor the swap usage during normal use you will see that it's very close to empty at all times and can't possibly free any RAM for programs (the only way of enhancing performance). So, to conclude, the 'enhanced performance' is all in the imagination. That doesn't mean the feature shouldn't be used (after all, I use it myself now), but it does come with a cost: You can't export the card through USB as long as you use it.