Cannot Generate SSPI Context - When changed Service Account - SQL Server 2008

I changed the service account used for MSSQLSERVER from Local System to a domain user account (domain\sql server)

When connecting to SSMS from my workstation, it came up with an error:

Cannot Generate SSPI Context - SQL Server 2008

If i connected using the SA account, I could get in, however, if I tried to save changes to my Maintenance Plan, it came up with the same error. (I'm sure there would be other operations that cause this error, I just used this as an example)

I also noticed I couldn't start SQL Server browser - Pops up error message:

the service cannote be started, either because it is disabled or because it has no enabled devices associated with it. [0x80070422]

I am using SQL Server 2008 Standard and Windows 2008, in case that is important....

Does your domain user have access to the folder where the physical files are stored?