[MOSS2007] Error while opening Site Columns page (/_layouts/mngfields.aspx)

[ISSUE]
When you open the Site Columns page (/_layouts/mngfields.aspx, Site Settings > Site Columns) SharePoint throws an "Unknown Error" at you.

When you change the CustomErrors=Off and CallStack=true values in the web config, SharePoint shows you the following error:
Object reference not set to an instance of an object.
at Microsoft.SharePoint.ApplicationPages.FieldListRenderer.Render(HtmlTextWriter output)
at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter)
at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter)
at System.Web.UI.Control.RenderControl(HtmlTextWriter writer)
at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer)

[CAUSE]
This issue is caused by the fact that a feature creates site columns using the incorrect casing in the url. For example:
http://<site url>/sites/Test instead of http://<site url>/sites/test
http://<site url>/Sites/test instead of http://<site url>/sites/test
source

[SOLUTION]
To determine which site columns are causing this issue:

• Open a sub site and open Site Columns of that site
• To the left of each column, the location where they have been created is shown
• Hover over links pointing to the parent site and check URL to which the link is pointing
• One or more URLs will have incorrect casing.

To solve this issue, you either have to change your feature so that it uses the internal URL which SharePoint is using. In my case, the feature that caused this issue was the "Office SharePoint Server 2007 Enterprise Site Collection Feature". In other words, some code I could not change.

I found an article on the Internet where they mentioned changing the site url in the database. I know database changes are not supported by Microsoft, but there was no other way to change this.

• Open the Content Database
• Open the table ContentTypes
• Check the column Scopes, you will find some URLs with the correct casing and some with incorrect casing. Change the casing of the incorrect records.