I might have been using an old version.
I'll close this, and reopen if it happens again.

It works here on my end. Even if I do a separate preprocessing experiment first. 
I remember that I have run into this error before too, but the latest code 
version should not copy the old properties file into the new run directory. Are 
you maybe using the same directory for the preprocessing? Normally the scripts 
append an "-p" to the given directory name.

I'm pretty sure I used the latest version (unless something has changes in the 
last 3 days or so).
Malte - I'll keep you in the loop.

are you sure you used the latest version of the new-scripts for the experiment?

Sometimes, the properties file created by downward_experiments contains 
two lines of - command_start_time (I think this is when preprocessed tasks are 
used).
This causes downward-resultfetcher to display an error message (from configobj).