Many have had problems provisioning the User Profile Service in SharePoint 2010, including myself.
My Powershell script failed and afterwards trying to manually create a User Profile Service Application in CA, I got the following error
An object of the type Microsoft.Office.Server.ActivityFeed.ActivityFeedUPAJob named "User Profile Service Application_ActivityFeedJob" already exists under the parent Microsoft.Office.Server.Administration.UserProfileService named "". Rename your object or delete the existing object.
Sounds like a Timer Job, so I wanted to take a look at the job definitions.
But now I got a "Operation is not valid due to the current state of the object".
OK, so I clearly needed to cleanup the Timer Jobs related to the User Profile Service. To do that I executed the following Powershell command.
Get-SPTimerJob | where {$_.name -match "User Profile Service*"} | % { $_.Delete()}
Now I was able to both review the job definitions and provision the User Profile Service Application successfully.