The combination of mixed case email addresses like Gern.Blanston@domain.com, Workspace 1.8 and the new SSO features seemed to break the ability to download files via the Workspace web page.
When users logged into Workspace and tried to download a file they were be redirected to a web page with the following:
HTTP Error 500- Permission Denied messages.
Contact VMware Support for the hotfix. For me, it was replacing the horizon-persist-0.1.jar file in the /opt/vmware/horizon/horizoninstance/webapps/SAAS/WEB-INF/lib/ folder in the service-va appliance.
Replacing the file and restarting the horizon-frontend service fixed the problem immediately.