IT WORKS!!! Thank you Elias! It wasn’t exactly what you suggested, but you gave me the right hint: I don’t have the addonpack installed (yet) and I didn’t rename the folder freeframe to freeframe_disabled, because there simply was no such folder. However there was one called freeframes (plural), which I renamed to freeframe, and now it works. Seems like that little s caused all the trouble. Though that makes me wonder how it can work for some users and for others it doesn’t (?)
Anyway, I can finally start exploring vvvv. Thanks a lot!