Black screen after initial splash with USB HDD connected when launched using haxchi

[Ailuros]

When I run this via regular haxchi (not cbhc) without an HDD connected it runs fine. But when I run it via regular haxchi with an HDD connected I get a black screen after the initial splash screen that has the credits/brick warning. The Gamepad responds (at least the TV button) but nothing else does. I have to do a hard shutdown. If you could fix this I'd greatly appreciate it because I'm unable to move saves between NAND and USB without copying each game in its entirety.

[Ailuros]

I've tested a clean SD card with just the latest Mocha, Homebrew Launcher, and SaveMii Mod from another person whose setup works. I completely reformatted my SD card to remove redNAND (FAT32 with 64k clusters) as well. My USB drive works fine, and its Y-cable has worked fine with several other drives and consoles. There are no Mac invisibles (._ files) on the card. And the lock switch isn't engaged (card is not write protected). I can't explain this.