VGA signal drops upon booting to Dreamshell

[Mu.]

As the title says, when I use my new VGA cable with my monitor or TV via a VGA -> HDMI adapter I'll get past the bios just fine but as soon as I see the Dreamshell logo (or even before then) the video signal will drop out.

I'm not sure what I've done wrong since I was previously able to use my cable with a VGA monitor just fine for several days. It wasn't until recently that this started happening.

I've copied over a fresh install of DS and that hasn't solved the issue, I'm unsure of what else I can do.