At the risk of sounding obvious, I'll say it anyway. Once you drag your pictures from the memory card to the Trash, you must EMPTY the trash to free up the space on your card.

Correct. The moral of the story: EMPTY the Trash.

This is like a Windows newbie mistake. I knew a woman who took her PC in for repair, it slowed down to a crawl and stopped working. It turned out she'd been throwing things in the trash for 2 years and never ONCE emptied the trash. So her disk was totally full. The PC repair guy emptied her trash and charged her $35 for 2 minutes of work (1 minute 50 seconds of which was spent figuring out what was wrong).

Windows is supposed to empty old files in the Recycling Bin when the drive reads 90% full. So there was actually something wrong with that computer other than just needing to empty the Recycling Bin.

Not 100% sure, but I think OS X will also delete old files from the Trash automatically when the disk space gets low. I think it's moronic to *make* people manually empty the trash.