Thanks for your replies.
We have tried installing generator in a new folder a couple of different times. We have completely deleted and reinstalled but nothing works.
Also, we have installed generator on 5 other web sites, so we're pretty confident that we know what we're doing there.
Could it be a licensing issue? We did buy a separate generator for each URL that we use it with, so I don't see why that would be an issue, either, but thought I'd ask.