svn mkdir --> Conflict - what can cause this?

We have an automatic (Hudson) build that runs every night. It starts by making a tag directory into which it will then copy the current build root folder. Last night, the mkdir failed:

svn --username [obfuscated] --password [obfuscated] --no-auth-cache mkdir --parents http://svn/repos/troux/autobuild/trunk/20110926_233057 -m"create autobuild tag directory"

svn: Conflict at '/autobuild/trunk/20110926_233057'

The job was rerun this morning without making any changes and it had no problem with the mkdir. I can guarantee that the directory didn't exist in the repository prior to the mkdir command.

The svn server is running on Linux (Fedora 14) and is at version 1.6.16
The client is on Linux (Fedora 14) and is at version 1.6.17

Ideas?
Received on 2011-09-27 16:56:53 CEST