When was QlikView server installed?
Don't you think the QlikView partner that installed it for you used a temporary key and now QlikView is just warning you that it will expire?
If you are able to open random .qvw's then it means you have a user CAL.
I would suggest phoning your QlikView partner and confirm that they have installed your license for you.
The issue is solved.
The pop-pup came from an add-on "ETL tools connector" which I had installed a while ago.
,Thanks to advice me to search somewhere else than in Qlikview