Cornstarch Clay Failure

A few years ago, the Lone Star Girl made little ornaments out of cornstarch clay for all her teachers, etc. for Christmas presents (this year, she's making them pot holders).  It was a great idea then, so the Lone Star Baby and I made a batch on Saturday, intended for her teachers. Something has gone awry, however.  It seemed to be working at the time, but the ornaments are all crumbly now.  I remember the ones her sister and I made taking days to dry but they did not crumble apart.  Hmmph.  Guess it's coffee gift cards for them. Hope they don't think coffee's evil.