ORA-24909 When Connecting to Oracle Database (4265104)

User can connect but when uses the Object Palette and select a schema/user which contains the tables wanting to query, generates the error message: ORA-24909:call in progress, Current operation cancelled

The error is immediate after it populates the list of tables.
Clicking "OK" to the error message, the tables display but trying to do any queries results in a not connected to Oracle error message.

Clicking on the "Views" tab in the Object Palette, generates "Database Error, Error trying to reestablish lost connection, Transaction already exists." The list of views is black except for a red "X" and "Toad for Data Analysis". Trying to go back to the tables list, another error message is displayed.