This applies to the nightly build (oct 10, 2011).

The safemode prevents to use the <%= shortname > and <= domain %> macros in a PXELinux template.

Here is the message shown by the UI when clicking the Build button for an host:

Failed to enable myhost.domain.tld for installation
Failed to generate PXELinux template: Safemode doesn't allow to access 'shortname' on #

The problem is gone when safemode is disabled.

Thanks.