SQL transaction timeing out problem

Hi i am using vb.net vs2008. I have a command object which executes a simple update statement on a table that has 100 000 records in it.
For some reason today it has started timeing out which it has not done before
I then took the UPDATE statement and ran it on SQL management studio and it is timing out there now as well.

UPDATE tblACBTrans set Status = 'Rejected' , UnpaidDate = '2009/07/02' where AutoID = 2829442;
I have created a separate Index non-clustered Unique index on my field AutoID which is also my primary key for this table. Still no joy

This is my code in vb to execute the statement, i tried setting the CommandTimeOut property to 60 but did  not help

       Dim command As New SqlCommand(SQLString, cn)
        command.CommandTimeout = 60
        Try
            If cn.State = ConnectionState.Broken Or cn.State = ConnectionState.Closed Then cn.Open()
            If cn.State = ConnectionState.Open Then
                command.ExecuteNonQuery()
                ModifyData = "Success"
            End If
       Catch exSQL As SqlException
         msgbox exsql.message.tostring
        Finally

            command.Dispose()
            command = Nothing
        End Try

thanks, any help would be great

thanks