Hi Rod,
thanks for your helpful answer and making me aware of the storage place. Indeed, I have changed location within the same building last week, but the default locations from captivate are local (C:\Users\...). I can tell this because - strange - I could open it again.
I just tried again because there was an updaet in the background telling me that I am on version 7.0.0.118 and that this update was just implemented 10 minutes ago.
I don't know if this success has got anything to do with the update, but it finally works ;-)
Kind regards!