It crashes in two different ways, depending how I try to enter fullscreen.

1. If I try to switch to fullscreen from within the game after starting it windowed, the application just dies. No error window or anything.

2. If I edit my config file so that the game launches in fullscreen, it crashes with an error report. I've uploaded two ZIPs to my Mediafire account; one from trying this with the Hell on Earth Starter Pack, one from trying with the base Brutal Room v20b download, in both cases attempting to load DOOM.WAD from The Ultimate Doom.

Hell on Earth: http://www.mediafire.com/file/pszrddo90njn02c/CrashReport_101216.zip
Base Starter: http://www.mediafire.com/file/v15zi1ld3r8o5r5/CrashReport_Starter_101216.zip

Are you sure it is a Brutal Doom crash? Only it sounds more like the engine (GZDoom) is crashing, rather than Brutal Doom, as BD is just a mod to the game, and I wouldn't see how fullscreen, windowed, or resolution settings would affect this.

Good point, I guess I didn't differentiate. It's probably a GZDoom crash. The verisons used in each case are...

Hell on Earth Starter Pack: Whatever's bundled with it
BD Core Starter: GZDoom 2.1.0 (March 2nd, 2016)

Another thought (but possibly an unlikely reason), but is the fullscreen resolution one that is supported by your screen? It's not a case of trying to use 1920x1080 on a 1680x1050 display or something like that is it?

Always a good question.

I'm sure it's not an incompatible resolution problem. I've tried 1280x720 and 1366x768, both of which are supported by both my laptop screen and the TV I have it connected to via HDMI. I've also tried toggling to fullscreen with only one screen or the other enabled.

One thing I did find is that if I switch to fullscreen with my resolution at something low-end like 640x480, it toggles properly, and then I can switch to a higher resolution and it will still work. But once I exit and try to start it again, it crashes on start.

And it's doing this just when Brutal Doom is being used, or does it do the same if you are just using DOOM.WAD with no addons?

It still sounds like it might be GZDoom to me, as I've never experienced Brutal Doom having such an issue. Have you tried using different versions of GZDoom? (But be warned, newer versions will require you to fix (though there are mods available that do this for you) the coding error in BLOOD.TXT within the Brutal Doom PK3 file). And have you tried updating your graphics drivers in case it is a drivrt or an OpenGL incompatibility/issue?

is it possible that the stress of how you have brutal doom set up causing an issue? Are you using a "Hi-res" texture pack a blood decal add-on & or have an "over the top" blood setting or have the "janitor" option disabled?

Doom may be over 20 years old but if you're not careful it can still be a bit much even on a modern 'puter

Yeah, GZDoom will tax your computer on certain mods because of the sheer amount of awesome it can do. And particles. It's one of the many reasons why I keep ZDoom around. Try turning off stuff like filters if you have them (Doom+filters outside of a nearest mipmap never really looked good to me anyway). Or since we're talking OpenGL and fullscreen issues [insert check your driver updates thing here].

Of course, since we're talking about BD here there's that .0001% possibility... but this to me doesn't sound like it's causing the issue.