We have had confirmation from Apple that this was an OSX bug and should be fixed in the latest Mountain Lion update. From Apple:
We believe this issue has been addressed in OS X Mountain Lion 10.8.2. The GM
version is available now. Please verify this issue and update your bug report
with the results.
OS X 10.8.2 build 12C54
Posted Date: September 19, 2012
http://support.apple.com/kb/DL1581
Wim