Restoring a XML site backup into 3.3 fails with "No enum const class..." exception

When restoring a XML site backup generated in 3.3, the restore process fails with the following exception:

2010-07-19 09:33:59,161 ERROR [Importing data task] [confluence.importexport.actions.ImportLongRunningTask] runInternal Failure during import
– url: /admin/restore.action | userName: admin | referer: http://localhost:8080/admin/backup.action | action: restore
com.atlassian.confluence.importexport.ImportExportException: com.atlassian.confluence.importexport.ImportExportException: Unable to complete import: Error while importing backup: No enum const class com.atlassian.confluence.search.service.ContentTypeEnum.blogpost
at com.atlassian.confluence.importexport.xmlimport.BackupImporter.importEntities(BackupImporter.java:323)
at com.atlassian.confluence.importexport.xmlimport.BackupImporter.importEverything(BackupImporter.java:275)
at com.atlassian.confluence.importexport.xmlimport.FileBackupImporter.importEverything(FileBackupImporter.java:103)
at com.atlassian.confluence.importexport.xmlimport.BackupImporter.doImport(BackupImporter.java:107)
at com.atlassian.confluence.importexport.xmlimport.FileBackupImporter.doImport(FileBackupImporter.java:45)
at com.atlassian.confluence.importexport.DefaultImportExportManager.importAs(DefaultImportExportManager.java:74)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:304)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at $Proxy77.importAs(Unknown Source)
at com.atlassian.confluence.importexport.actions.ImportLongRunningTask.runInternal(ImportLongRunningTask.java:55)
at com.atlassian.confluence.util.longrunning.ConfluenceAbstractLongRunningTask.run(ConfluenceAbstractLongRunningTask.java:21)
at java.lang.Thread.run(Thread.java:613)
Caused by: com.atlassian.confluence.importexport.ImportExportException: Unable to complete import: Error while importing backup: No enum const class com.atlassian.confluence.search.service.ContentTypeEnum.blogpost
at com.atlassian.confluence.importexport.xmlimport.DefaultXmlImporter.doImport(DefaultXmlImporter.java:55)
at com.atlassian.confluence.importexport.xmlimport.BackupImporter.importEntities(BackupImporter.java:314)
... 19 more
Caused by: java.lang.IllegalArgumentException: No enum const class com.atlassian.confluence.search.service.ContentTypeEnum.blogpost
at com.atlassian.confluence.importexport.xmlimport.parser.BackupParser.endElement(BackupParser.java:53)
at org.apache.xerces.parsers.AbstractSAXParser.endElement(Unknown Source)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanEndElement(Unknown Source)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(Unknown Source)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
at org.apache.xerces.jaxp.SAXParserImpl.parse(Unknown Source)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:176)
at com.atlassian.confluence.importexport.xmlimport.DefaultXmlImporter.parseBackup(DefaultXmlImporter.java:83)
at com.atlassian.confluence.importexport.xmlimport.DefaultXmlImporter.doImport(DefaultXmlImporter.java:47)
... 20 more

For another customer, a different error was reported:

2010-07-19 07:30:00,476 ERROR [Importing data task] [confluence.importexport.xmlimport.DefaultImportProcessor] persist Error while saving object: Imported[com.atlassian.confluence.mail.notification.Notification] [Id[id]=2621442, Property[page]=com.atlassian.confluence.pages.Page[Id[id]=2555910], Property[userName]=amiller@dnscoinc.com, Property[creatorName]=amiller@dnscoinc.com, Property[creationDate]=2009-09-15 14:25:26.000, Property[lastModifierName]=amiller@dnscoinc.com, Property[lastModificationDate]=2009-09-15 14:25:26.000, Property[digest]=false, Property[network]=false, Property[type]=com.atlassian.confluence.search.service.ContentTypeEnum[]]

• referer: http://localhost:8080/setup/setup-restore-start.action | url: /setup/setup-restore.action | userName: anonymous | action: setup-restore
  2010-07-19 07:30:00,478 ERROR [Importing data task] [confluence.importexport.xmlimport.BackupImporter] importEntities Cannot import the entities:
• referer: http://localhost:8080/setup/setup-restore-start.action | url: /setup/setup-restore.action | userName: anonymous | action: setup-restore
  com.atlassian.confluence.importexport.ImportExportException: Unable to complete import: Error while importing backup: No enum const class com.atlassian.confluence.search.service.ContentTypeEnum.
  at com.atlassian.confluence.importexport.xmlimport.DefaultXmlImporter.doImport(DefaultXmlImporter.java:55)
  at com.atlassian.confluence.importexport.xmlimport.BackupImporter.importEntities(BackupImporter.java:314)
  at com.atlassian.confluence.importexport.xmlimport.BackupImporter.importEverything(BackupImporter.java:275)
  at com.atlassian.confluence.importexport.xmlimport.FileBackupImporter.importEverything(FileBackupImporter.java:103)
  at com.atlassian.confluence.importexport.xmlimport.BackupImporter.doImport(BackupImporter.java:107)
  at com.atlassian.confluence.importexport.xmlimport.FileBackupImporter.doImport(FileBackupImporter.java:45)
  at com.atlassian.confluence.importexport.DefaultImportExportManager.importAs(DefaultImportExportManager.java:74)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  Caused by: java.lang.IllegalArgumentException: No enum const class com.atlassian.confluence.search.service.ContentTypeEnum.
  at com.atlassian.confluence.importexport.xmlimport.parser.BackupParser.endElement(BackupParser.java:53)

Steps to replicate:

1) Startup a fresh/clean 3.3 Confluence instance.
2) "Follow" a user (for testing, I had added myself as a follower - user "admin")
3) Check the "Subscribe to Network" and "Notify on my actions" checkbox under "User Preferences"
4) Watch a page in any space. For testing I had set a watch for one of the pages in the "Demonstration Space".
5) Generate a site XML backup
6) Restore the above backup either via the setup wizard or via the "Administration" console.