請問這個錯誤訊息是什麼....(編號:5487)

ADODB.Recordset 錯誤 '800a0e7d'
The application requested an operation on an object with a reference to a closed or invalid Connection object.
/abc/abc.asp, 列30
列30行是下段的程式碼,有什麼錯嗎?
rj.open"select * from Book_data where Book_id ='" &_
request("txtbk_id") & ""',cnndb

請各位高手們...幫幫我吧..