Hi Mike,

A few things to try:

1). Make sure to stop the SQL Server Agent service before connecting to the
instance. If you have it running it uses the connection blocking your
access.
2). Use sp_who to find the session ID of the active connection and use KILL
to terminate it.
3). If all fails you can open a dedicated administrator connection:
http://msdn2.microsoft.com/en-us/library/ms189595.aspx

HTH,

Plamen Ratchev
http://www.SQLStudio.com