I've had the same error message pop up intermittantly on some of my agents. Were you ever able to get a solution to this issue?
I would check certificate file .0 existence, i mean that: on the client, in folder c:\Program Files\LANDesk\Shared Files\cbaroot\certs\ it should exist the same xxx.0 file that you have in core server share ldlogon \\coreserver\ldlogon\xxx.0 ;
Try to copy the one you have in the core on the client and retry the task.
Maybe something went wrong and you need to redeploy your 8.8 client configuration.