I'm experiencing the same issue here since the upgrade from RC3 to RC4.
1. Dashboard view, opening the logs of a VM or Docker opens an empty window that never gets filled
2. Dashboard view, click on unraid log opens an empty window as well
3. Docker and VMs views, opening logs has the same result, a white window with no info
Command line does work
/usr/bin/tail -n 42 -f /var/log/syslog 2>&1
/usr/bin/docker logs --tail=350 -f PlexMediaServer 2>&1
...
Tested with Firefox 38 and IE 11