Symptoms

1. Attached images are not shown in RoundCube;
2. Images could be downloaded by pressing the Download button. However, they could not be opened on the filesystem;

3. When trying to view an image with enabled firebug the following errors appear:

   Resource interpreted as Document but transferred with MIME type image
   

or

    Image cannot be displayed because it contains errors

1. Hexes of the sent and downloaded images differs: the downloaded one has some additional bytes at the beginning of the file.

Cause

Syntax error in one of the RoundCube's scripts.

Resolution

Check all customized ".php" scripts in /usr/share/psa-roundcube/ . If it is possible, compare the installed RoundCube with the test one. Try to find additional closing tags, carriage returns etc.