Antivirus software or other other real-time system scanning utilities may cause disruption if files needed by QlikView services are being locked for scanning / change monitoring. When using Certificate Trust for services authentication, the certificates may have expired or removed on the server running the QlikView Management Service (QMS). This will prevent the QMS from reading encrypted data in the QVPR, such as passwords (used in tasks and other areas of the QMC), resulting in the error message.
The log entry itself does not reference the "bad data", only a string length of the problematic string, which does not help in narrowing down the malformed data and correct it. Furthermore it is not advised to manually edit the QVPR and doing so will result in an unsupported environment.