This type of 404 error can occur sometimes if the connection in DW is corrupted or not working correctly. One thing that you could try to do while DW is closed is to open the site root and find the _mmServerScripts folder. Copy this folder to a different location on your hard drive and delete the copy that is in your site folder, then open DW and attempt to interact with the recordset. There are some recordsets within the PowerStore that are there by default that you will not be able to edit due to their complexity, but you should be able to edit any recordset that you have created. If you still have problems with it you may need to delete the recordset and start over again with it.