There seems to be a bug in xfire (www.xfire.com) that causes the deck editor to lose all the cards except for that one aqua card.
If I close down xfire, the cards appear. Run it, the cards disappear. On / off on / off.
So, to fix the Magic The Gathering: Planes of Shandalar / Spells of the Ancients / Duels of the Planeswalkers invisible / missing cards in the deck editor (deck.exe) problem, I simply closed down good ol' xfire.
None of my other utils (AIM, Logitech joystick applet, kerio firewall, mIRC, etc) caused a problem, nor my Nvidia drivers for my geforce 5200. (Although I did fiddle with the applications specific settings, forcing antialiasing, ansiotropy, etc etc to off, not that I think that was to blame. Can't be bothered to set it back though)