The autoenrollment functionality fails when a Windows Vista-based computer uses version 2 (V2) certificates. Additionally, an event that resembles the following is logged in the Application log:

Log Name: Application
Source: Microsoft-Windows-CertificateServicesClient-CertEnroll
Date: Date
Event ID: 13
Task Category: None
Level: Error
Keywords: Classic
User: User SID
Computer: Computer Name
Description:
Certificate enrollment for Local system failed to enroll a template certificate from certification authority. (The RPC server is unavailable. 0x800706ba. (Win32:1722))