Today I wanted to do some research in my lab environment for a customer. However, after start SQL Server Agent 2012 I got an error. In the Event Viewer I saw the following error:

OpenSQLServerInstanceRegKey:GetRegKeyAccessMask failed (reason: 2).

After Googling I tried some solutions but they didn’t work. In my case I changed the serviceaccount of the agent. After changing the Agent did start and I was able to perform SQL Jobs.