Database Keeps Showing As Suspect...

I am currrently working on a ASP.Net 2.0 project using Sql Server 2000 with SP4. Whenever I run any query the connected database keeps showing as 'Suspect' and I can't access it from Enterprise Manager/ Query Analyzer. But my ASP.NET pages work fine. I can access my records as well as update them through my ASP pages.
Please help me out....
Here is the code which I use in my ASP.Net page

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Dim selectsql As String
selectsql = "select au_fname FROM Authors"
Dim con As New SqlConnection("Data Source=.SQLEXPRESS;AttachDbFilename=""C:Program FilesMicrosoft SQL ServerMSSQLDatapubs.mdf"";Integrated Security=True;Connect Timeout=30;User Instance=True")
Dim cmd As New SqlCommand(selectsql, con)
Dim ass As SqlDataReader

Try
con.Open()
ass = cmd.ExecuteReader
Do While ass.Read
Dim newitem As New ListItem()
newitem.Text = ass("au_fname")
'newitem.Value = ass("zip")
ddl.Items.Add(newitem)
Loop

ass.Close()

Catch ex As Exception
lblmsg.Text = "error has occured "
lblmsg.Text &= ex.Message

Finally
If (Not con Is Nothing) Then
con.Close()
End If
End Try
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