While we have no idea why this is the case, my incredible Zope hosting dude, David Elkins (hurrah.com) and I managed to get my code working so that I can now create instances of my own ZClasses reliably. We only did two things. We took the code that should have worked and didn't, copied it, and pasted it into a new DTML Method object with a different name (we called it 'test' instead of 'startClearing'). We restarted the back end of the Zope server. Now it works. It even works in its original form and name. No clue why. Frankly, only mildly interested in the reason. It works. I must, however, say that this has shaken my confidence in Zope a bit even though I am acutely aware that there could be dozens of non-Zope reasons for this to happen. This was just too weird and it cost me 21 unbillable hours. Weird.