Minor issue with Aldiko reader and calibre-server

I'm running calibre-server and I can successfully connect via a regular browser. However, I have a minor issue accessing calibre-server from the Android Aldiko reader. In principle I can access calibre-server but it does not load images (such as the calibre.png logo at the beginning of the page). The funny thing is that cover art *is* shown, just not the decorative buttons that are on the page served by calibre-server. I am using a reverse proxy so I can use SSL.

Anyone has come across this before?

Arno