I just spent 3 hours looking into this further and trying to fix the problem, and I cannot get it to work.

I find it distressing that the creator of the mod fails to respond. I understand that no support is guaranteed, but 3 or 4 people with the same problem shows that something is slightly different on the developer's system. On his system, the yclass or _yclass is being properly instantiated; on ours, it is not.

I don't know enough about the inner workings of Zen Cart to get further than that.

Does anyone know how to go about uninstalling this mess?