[Zope] Zope on CD

Hello List, we need to set a Zope-Installation to read-only to start from cd. It's Zope 2.10 We set the following directives on zope-conf. read-only-database on zserver-read-only-mode on enable-product-installation off Then we a custom_zodb.py in %INSTANCE_HOME% Sometimes Zope starts and sometimes it alerts "Permission denied" - "Data.fs.lock" Does anybody know what could be the problem? Many thanks in advance, Ulla.