[Inf-IT DAVcl] suddenly 403 for config.js

I just realized that my infcloud Installation does no longer work. In the javascript console, I can see:

Failed to load resource: the server responded with a status of 403 () for config.js

- checked the file permissions and it is 644 (folder infcloud is 755) with correct owner. As I did not change there anything recently, I wonder what might be the Problem ? any hints appreciated. (infcloud version appears to be 0.13.1)