Getting an access violation before main starts

[Matt via Digitalmars-d]

I was wondering if anyone could help with a problem I'm having.

My program compiles properly, and has all up-to-date files and 
DLLs (SDL2, SDL2-image, SDL2-ttf, all the other DLLs that are 
required by these). However, when I run it, I get "object.Error: 
Access Violation", which, of course, means something isn't 
getting created.

I'm using dub to build (although I get the same problem when 
trying to build manually).

My main program looks like this:

---


void main (string[] args){
	Window window;
	JSONValue cfg;
	Input input;
	
	try{
		window = new Window ();
		cfg = loadConfig;
		
		window.create (cfg["window"]["caption"].str, to!int 
(cfg["window"]["width"].integer), -1, -1, to!int 
(cfg["window"]["height"].integer), 
(cfg["window"]["windowed"].type == JSON_TYPE.FALSE) ? true : 
false );
		window.releaseMouse;
		
		input = window.getInput ();
	}
	catch(Error e){
		writeln ("error occurred before timing variable setup");
		return;
	}
	
	
	
	// set up timing variables
	auto duration = TickDuration (cfg["graphics"]["ticks"].integer);
	
	auto current_tick = Clock.currAppTick;
	auto target_tick = current_tick + duration;
	auto target_margin = target_tick + (duration/2);
	
	// main loop
	try{
		while (!window.is_dead){
			auto keys = input.getKeyboardState ();
			
			/// TODO: there is a range error occurring in keys.keys when 
holding down left alt. Check for other modifier keys
			if (/*(keys.mods & 
KeyMods.LeftAlt)*/keys.scans[ScanCode.LeftAlt] && 
keys.scans[ScanCode.F4]){
				window.destroy;
				break;
			}
			
			current_tick = Clock.currAppTick;
			if (current_tick >= target_tick){
				// this way, it will wait for the next frame, if there is 
less than half the time to the next frame left
				if (current_tick < target_margin){
					// update graphics and physics
				}
				// prep for next tick
				target_tick += duration;
				target_margin += duration;
			}
			
		}
	}
	catch(Error e){
		writeln ("error occurred during main loop");
	}
}

---

Both Window and Input are my own classes, which I've checked for 
leaks, and don't appear to have any. They are basically wrappers 
around SDL functionality. I can include the source if people 
want, but it's pretty long.

The try-catch blocks were put in to see if I could track down 
which part of the code the error's occurring in, which is why I 
believe it to be happening before main() is called.

I'd appreciate any help that you guys can give, and many thanks 
in advance.