Our SharePoint 2010 started crying late last Friday, of course right when I wanted to leave, and first thing this morning I took a look at the server and found the following errors:

Load control template file /_controltemplates/TaxonomyPicker.ascx failed…

Fortunately, I’m not the only one who seems to have had this problem pop out of the blue.  I found a solution fairly quickly here.  To summarize, here’s what you do:

On the server, navigate to C:program filescommon filesmicrosoft sharedweb server extensions14TEMPLATESCONTROLTEMPLATES and open TaxonomyPicker.ascx in notepad.  towards the top you will see the following line:

<%@ Control className="TaxonomyPickerControl" Language="C#" Inherits="Microsoft.SharePoint.Portal.WebControls.TaxonomyPicker&#44;Microsoft.SharePoint.Portal, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>

Change the , to a comma (,), so now the element will look like this:

<%@ Control className="TaxonomyPickerControl" Language="C#" Inherits="Microsoft.SharePoint.Portal.WebControls.TaxonomyPicker,Microsoft.SharePoint.Portal, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>

Save the file.  No need to restart IIS or any web services, app pools, nothing.  Not sure why it did that, but it did, and this fixed it!

Hope this helps someone else!

UPDATE: If this doesn’t help, try renaming the file to TaxonomyPicker.ascx.broken.  Apparently the control isn’t even used and this will force the App Pool to ignore it when refreshing.