SHAREPOINT:The list that is referenced here no longer exists

Are you get this error while using the updatelistitems method in SHAREPOINT web service (list.asmx)?
Are you aiming to data stored in a subsite?
If so, the solution is to point the webservice of the subsite directly.
If your main site is http://cia, and your subsite is http://cia/coa, you should point to the webservice:

http://cia/coa/_vti_bin/list.asmx

Pay attention that, sometimes, when you update the webreference, in the app.config it remains the same. So change it there as well.

Good luck!