I have Xubuntu 16.04 installed as the only OS on my Acer Aspire 5750 laptop. I have a BenQ external monitor connected such that I have a dual monitor setup (my laptop screen + BenQ).
When the BenQ monitor, connected to my laptop via HDMI, is not receiving a signal (which happens when the computer is off), it displays a message "HDMI No Cable Connected!" and presumably goes into some idle mode. When it is in this mode and I turn on the computer, the boot hangs and I see the Acer logo covered partially by a black rectangle's silhouette:
I set GRUB_CMDLINE_LINUX_DEFAULT="" in /etc/default/grub to attempt to see the boot messages, but nothing can be seen - the computer really freezes at boot. If I proceed by turning off the computer forcibly (hold the power button for 5 seconds) and quickly turn it back on again, which avoids the BenQ monitor from going into its idle mode and the boot sequence proceeds successfully. If I unplug the monitor and use my laptop's screen only, boot works nominally.
My question: what can I do to fix this boot freeze? Thanks for any suggestions!