Error on submission of 'Member Signup and Renewal' form

Non-recoverable error on final submission ('Make contribution') of this
form in test-drive mode -

Error Details:

Array
(
[callback] => Array
(
[0] => CRM_Core_Error
[1] => handle
)

[code] => 536870966
[message] =>
[mode] => 16
[debug_info] =>
[type] => PEAR_Error
[user_info] =>
[to_string] => [pear_error: message="" code=536870966 mode=callback callback=CRM_Core_Error::handle prefix="" info=""]
)