Has been working for months now ...

Using the Administration user interface to create an Export :

Form Errors:
An exception occurred backing up: com.atlassian.core.AtlassianCoreException: Error in action: <a href='mailto:com.atlassian.jira.action.admin.DataExport@159a690'>com.atlassian.jira.action.admin.DataExport@159a690</a>, result: error<br> Error exporting: java.io.IOException: The character '�' is an invalid XML character

The export service now is unable to export (neither using the administration user interface).
Is there a way to figure out which data is incorrect?
Turned on debugging (will attach log) on the server but could not figure out.

Looks like an encoding problem. We are using ISO-8859-1 in Jira and the Oracle9i database.