Hi Jason,
Yes this is something that we have already seen with Windows Security Essentials or Windows Defender. Disable it helps a lot with the KES installation.
Also, you might be interested in the following article, in order to help you out in tricky occasions:
http://community.landesk.com/support/docs/DOC-29203
If you still have issues with the AV install, please raise a case with the support we will help you narrow down the cause of this issue.
Regards,
Jonathan