Hi John,
This thread should be address your query : http://www.petenetlive.com/KB/Article/0000985.htm
In case it does not help, please run this following service http://kb.eset.com/library/ESET/KB%20Team%20Only/Malware/ServicesRepair.exe and try to install the client.
Lastly, you might want to confirm the anyconnect package being pushed to the client is not corrupted and try to upload a new package from CCO and try again.
Please let me know how it fares.
Regards,
Dinesh Moudgil
P.S. Please rate helpful posts.
Cisco Network Security Channel - https://www.youtube.com/c/CiscoNetSec/