I have a specific action, extending the EditPageAction class. This action has a parameter named 'meta'.
I've overridden the 'doEdit' method to check if this parameter 'meta' has been set.
Here is a snippet of the code:
if (log.isDebugEnabled())
log.debug("Entering");
boolean isHandy = (meta != null) && (!meta.equals(""));
if (log.isDebugEnabled())
log.debug((isHandy ? "is handy" : "is not handy"));

Now the logs I have 'sometimes':
2009-03-24 10:35:46,444 DEBUG [WebContainer : 37] [capgemini.confluence.handymetadata.EditHandyAction] setMeta Setting meta to <metadatalist><metadata><name>Id</name><type>text</type><list></list><mandatory>true</mandatory><value>ab14451</value><readonly>true</readonly></metadata>...</metadatalist>
2009-03-24 10:36:25,716 DEBUG [WebContainer : 37] [capgemini.confluence.handymetadata.EditHandyAction] doEdit Entering
2009-03-24 10:36:25,723 DEBUG [WebContainer : 37] [capgemini.confluence.handymetadata.EditHandyAction] doEdit is not handy

It looks as if the content of the 'meta' parameter was lost between the time when the setter was called and the taime the doEdit method was called

Problem solved: was due to user misbehaviour