Yes, I solved it. I don't remember how I installed it but strangely my installation missed ONLY this qhelplink.h and QHelpLink. How strange!
No, it's more likely that you are using a module that isn't that much used by the members of the forum.
You can also bring that question to the interest mailing list. You'll find there Qt's developers/maintainers. This forum is more user oriented.
Ah, that seems to have done the trick. Still curious about why that particular module needed to be manually linked but others didn't, but hey it works, so many thanks.
@SGaist Sure! :)
I updated my previous post since I solved part of the issue.