Exception error while activating Sharepoint Publishing feature

Issue:

Whenever you try to activate the "Office SharePoint Server Publishing Infrastructure" feature from site collection, it throws the following error message.

Exception Error 0x80020009

Solution:

Try to activate through command line

stsadm -o activatefeature -filename publishing\feature.xml -url http://URL -force

stsadm -o activatefeature -filename publishingresources\feature.xml -url http://URL  -force

stsadm -o activatefeature -filename publishingSite\feature.xml -url http://URL -force

stsadm -o activatefeature -filename publishingweb\feature.xml -url http://URL -force

stsadm -o activatefeature -filename publishinglayouts\feature.xml -url http://URL -force

stsadm -o activatefeature -filename navigation\feature.xml -url http://URL -force

Unable to create new page "Data at the root level is invalid. line 1 position 1"

Issue:

Unable to create new page in SharePoint 2007 subsite
Error:  "Data at the root level is invalid. line 1 position 1"

Resolution: 
1. Deactivate Office SharePoint Server Publishing feature from the affected subsite - Site features
2. Deactivate Office SharePoint Server Publishing Infrastructure feature from the top level site - Site Collection features
3.  Activate  Office SharePoint Server Publishing Infrastructure feature from the top level site - Site Collection features
4.  Activate Office SharePoint Server Publishing feature from the affected subsite - Site features

Hope this helps.