"Download updates while installing Ubuntu Studio" greyed out in installation dialogue

[Set Hallstrom]

Proceeding to install from a live-iso boot, being connected to my wifi (writing from that computer) having selected the wifi in the installation dialogue with the password correctly entered by the system from the network settings, i find the "Download updates while installing Ubuntu Studio" tick-box grayed out.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubiquity 2.21.51
ProcVersionSignature: Ubuntu 4.4.0-15.31-lowlatency 4.4.6
Uname: Linux 4.4.0-15-lowlatency x86_64
ApportVersion: 2.20-0ubuntu3
Architecture: amd64
CasperVersion: 1.368
CurrentDesktop: XFCE
Date: Thu Mar 24 19:58:14 2016
InstallCmdLine: file=/cdrom/preseed/ubuntustudio.seed boot=casper initrd=/casper/initrd.lz quiet splash --- debian-installer/language=sv keyboard-configuration/layoutcode?=se
LiveMediaBuild: Ubuntu-Studio 16.04 LTS "Xenial Xerus" - Beta amd64 (20160323)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=sv_SE.UTF-8
 SHELL=/bin/bash
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Anthony (danthonyd)]

Yes, I am testing a second 16.04 Xenial Xerus installation using a USB wifi adapter and the "Download updates while installing Ubuntu Studio" box is greyed out. I noticed as the DVD was booting there were 3 black screen level errors which cleared (displayed again then "went away") at the first power down. I didn't have the quick reflexes to take a photo of the error messages, and I don't want to start digging around for a log somewhere, but it may be related...