This is not a new problem and don't waste any time on it if you think it's unsolvable. For about a couple of years now, ever since my project files got too big, I have not been able to export to DHTML without problems. It's not a disaster but annoying nonetheless. The worst case scenario so far has been that all goes well until the end of the Powerpac export when I see this (see picture).

I may be completely wrong about this but I get the impression that it's been misbehaving more since the last Powerpac update but this could also be because my files have got slightly bigger again. In the future I will make sure to split content into several tbk files so that this cannot happen but I'm very close to completing work on the oversized files so I'm carrying on regardless.
It is something to do with the three export dialog windows that is causing the problem as if the last one has lost the focus and cannot complete the last phase of the process. If you can see a quick fix it would be nice but otherwise don't bother. I can live with it for a few weeks more.

John