There was an error during the callback and the PeoplePicker

I set up a cross-forest account (using stsadm) to search a domain for user accounts. This worked fine for the Farm Administrator account, but did not work for the account running the application pools for other Web Applications.

On these other Web Applications, when attempting to search for “foriegn_domainuser”, instead of receiving the user (or a list of matching users), I would get “There was an error during the callback”.

Running Filemon while performing this, I found that the account running the application pool did not have access to the following registry key:

HKLM\SOFTWARE\Microsoft\Shared Tools\Web Server Extensions\14.0\Secure

Once I granted the account access, the error did not return while using the PeoplePicker to search for users.

Trevor Seward is a Microsoft Office Apps and Services MVP who specializes in SharePoint Server administration, hybrid scenarios, and SharePoint Online. He has been working with SharePoint for 16 years from SharePoint 2003 on up, managing environments with terabytes of content for 150,000+ user organizations. Trevor is an author of Deploying SharePoint 2016 and Deploying SharePoint 2019. You can find him at /r/sharepoint.