This error occurs at the Salesforce side. Please refer to:
"Each Salesforce user can have up to 10 query cursors open at a time. This is a hard coded limit that cannot be increased. If 10 query locator cursors are opened when a client application attempts to open a new one, then the oldest cursor is released. If a call is attempted to an expired or released cursor, salesforce.com will return the INVALID_QUERY_LOCATOR error. To avoid this error, ensure that the client code is not holding open more than 10 query locator cursors. If multiple processes are running using the same salesforce.com user, make sure that their combined query locator cursor count remains at 10 or below."
Most likely, a lot of your packages run at the same time (other tools that use the same Salesforce account are also taken into account) and, thus, try to open more than 10 query cursors. Please try re-scheduling your packages.