It can take up to 3-4 minutes before a user is logged in to the Workstation.
TAC Vista 5.1.8
The problem is a combination between a Vista server network and many disabled alarms.
When logging on with a Workstation to a Vista server the server will read the disabled alarms from the other Vista servers in the TAC Vista network.
This is a slow process, in this case 5 Vista servers was connected in a Network and they all had around 2-300 disabled alarms.
Then it took 3-4 minutes for the workstation to logon to the Vista server.
Try to keep disabled alarms to a minimum in a Vista server network.
Don't have unnecesssary disabled alarms in the system.