Many, many posts can be found on the Internet regarding issues provisioning the User Profile Synchronization service with one of them being the Holy Grail :
Spencer Harbar’s Bible
2 of our 3 farms began to fail during the full farm backup procedure we perform every week. After looking in the ULS to check what was going on, it appeared that the UPSA failed to provision and was blocking the whole full farm backup.
The error found in the ULS was :
Event 9i1w : ILM Configuration : Error “ERR_CONFIG_DB”
After digging a while, I found out it was linked to the Powershell Module “PSReadline“.
I add installed WMF 5.1 on the servers and installed the module at some point. What I didn’t knew was that the module PSReadline is loaded in all and every powershell console once it has been declared. It doesn’t appears in the profile files but it is still loaded.
This module seems to be in conflict with the UPSA provisioning method and makes the FIM installation crash at provisioning.
Lesson learnt :
DO NOT EVER CUSTOMIZE THE POWERSHELL CONSOLE ON SHAREPOINT SERVERS !!!!