Sorry if it's not under the right category. I just want to know if it's a universal issue or just happening on my Mac. A couple of months ago, I wrote in another thread about a problem I was having that I couldn't boot my computer with external HDDs attached. As it turns out after months of testing, it only refuses to boot when a hard drive beyond 2TB is connected via USB. So if there is a 3TB HDD connected via Thunderbolt, it's perfectly okay. But if there is one connected via USB, then it won't boot. Just halt at the grey screen, and none of the peripherals (I use USB keyboard) will work. The problem persists even on the login screen. I have to wait till I see the wallpaper. I did some digging, and it turns out there is such problem very similar to what I'm having. But it only applies to PC. So, what could really be going on behind the screen?