The file doesn't exist (NSCocoaErrorDomain 4)

This started a few days ago. When I open DTPO, I get a little Log window with many entries, each of which reads “The file doesn’t exist”. Under Info, it says NSCocoaErrorDomain 4.

What is this and how can I stop it?

could you please choose Help > Bug Report (after pressing the Alt modifier key) and send the email to cgrunenberg - at - In addition, which version of OS X and DEVONthink do yo use? Does a restart of the computer fix this, is there enough disk space available on the startup volume?