I have recently came across very unusual error while accessing web part gallery link from the site settings page – Failed to find the XML file at location ’12\Template\Features\FilterByLocationDropDownList\feature.xml’ at Microsoft.SharePoint.SPXmlDocCache.GetGlobalXmlDocumentCore(String pathXml, Boolean bFeature) at Microsoft.SharePoint.SPXmlDocCache.GetGlobalXmlDocument(String pathAllFeaturesRelativeXml)

This seems like web parts links page is still referencing one of the previously installed feature – “FilterByLocationDropDownList”. This may have happened because feature never been uninstalled on the site and there might be still lingering references in SharePoint_Config database.

If you come across this issue, follow these steps to clean up the system.

Step – 1
In the WFE 12\Template\Features folder on all the WFE servers, copy any feature folder and rename it to <feature name> which causing an error message on the Workflow pages. Once you create the folder, if you refresh the workflow page, errors should be cleaned up and work flow page should work now.

Step – 2
Run the following query to get the corrupt feature ID

   1:  use sharepoint_config
   2:  select id, properties

   3:  from objects
   4:  where properties like '%<feature name>%'

Step – 3
Run the following from the WFE server to cleanup the lingering feature references.

   1:  stsadm -o uninstallfeature -id <id of the feature name>

Step – 4
Delete <feature name> folder on all the WFE servers to clean the system.

Hopefully this may help to focus on more productive stuff.