[O] Debugging background export

[Jacek Generowicz]

Greetings,

When I export the org file I am working on (C-c C-e b), everything  
works fine. When I try to export the same file in the background (C-x  
C-s C-u C-u C-c C-e b), I get the very informative messages

Background process "Exporting course.org<1>": started
Background process "Exporting course.org<1>": exited abnormally with  
code 255

What would be a good way to debug this?

Thank you.