No try/install dialogue displayed

[Elfy]

Running 32vivid Xubuntu in VBox running in vivid.

Boots to a blank desktop - should boot to our Try/Install Dialogue.

Only apparent in vbox, running the same image from usb on hardware and it works.

Reported this via vt1 and apport-cli

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: syslinux (not installed)
ProcVersionSignature: Ubuntu 3.18.0-13.14-generic 3.18.5
Uname: Linux 3.18.0-13-generic i686
ApportVersion: 2.16.1-0ubuntu2
Architecture: i386
CasperVersion: 1.351
Date: Wed Feb 18 17:21:14 2015
LiveMediaBuild: Xubuntu 15.04 "Vivid Vervet" - Alpha i386 (20150218)
ProcEnviron:
 SHELL=/bin/bash
 TERM=linux
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 XDG_RUNTIME_DIR=<set>
SourcePackage: syslinux
UpgradeStatus: No upgrade log present (probably fresh install)