Updating Text Fields

I am trying to update text fields where the field only has the value
"closed." So a field that has closed and anything else will not be
updated.


update dbo.Hist
set dbo.Hist.Notes = ''
FROM dbo.Hist
WHERE (Notes LIKE 'closed_')

update dbo.Hist
set dbo.Hist.Notes = ''
FROM dbo.Hist
WHERE (Notes LIKE 'closed%') and len(convert
(varchar(7000),notes)) = 7

Neither code works and i get this error: "Subquery returned more than
1 value. This is not permitted when the subquery follows =, !=, <, <=
, >, >= or when the subquery is used as an expression.
The statement has been terminated."

What's another way to make the update?