Since the last round of Microsoft patches I am getting a lot of;

Failed to process action: Length of the data to decrypt is invalid.

from my clients. This will repeat on the same random bundle over and over for days on end generating thousands of log entries.

The debug log file shows this and it shows it on extremely simple bundles too.

What causes this? I'm also upgrading to Symantec Endpoint Protection. Perhaps there is an exclusion I'm in need of?