Instead of showing up as /dev/sdx#, only the first partition of the memory card shows up, and it shows up as /dev/sdx. /dev/sdx can be mounted, and copying from the memory card works fine. Copying to the memory card doesn't work. It looks like everything is hunky dory, but the files are actually never saved on the memory card. Partitioning the memory card doesn't work either. Gparted shows the whole memory card as «unpartitioned». After creating partitions on the card, the phone cannot mount the card.
Google didn't help much either. Other people simply claim that the memory card is bad. I have a hard time believing that as a) it works fine in any card-reader I've tried it on, and b) it works fine in the HTC Desire it self and with the HTC Desire connected to any other operating system.
If anybody has any ideas what's going on here, I would really appreciate an email.