PC troubleshooting help needed.

So, I had a bit of a weird situation yesterday morning. I plugged my phone into my PC via USB, and the second it connected, my whole system just completely froze. Everything on the screen was totally stuck, though the tower itself seemed fine—no strange noises or anything, just total stillness. Naturally, I went to do a hard reset, and the computer rebooted like nothing happened. All the lights came on, everything sounded normal during the boot process, but my monitor just refused to cooperate. It would power on, show "no signal," and then immediately drop back into sleep mode. To troubleshoot, I tried plugging the PC into my TV using an HDMI cable, but even the TV gave me that same "no signal" error. The PC still boots up without any weird beeps or issues, and all the LEDs are lit, but I’m just staring at a black screen. It feels a little strange because I’ve never had a phone connection trip up my rig before.
If anyone happens to know what might be causing this or if there's a fix, I would seriously appreciate the help! Just to give you guys a better idea of what I'm working with, here are my specs:

AMD FX-Series X8 8300 AM3+
ASUS GA-970A-UD3P,AM3+
Crucial 8GB 1600 MhZ
Gigabyte R9 390 GAMING 8GB
SanDisk Z400s 128GB SSD
Dell Inspiron 1TB,high perf.
EVGA, 650W

Just wanted to add a quick note here—I'm actually running a DVI-D output from my graphics card, and I've got an HP 21.5-inch monitor hooked up to it. "

Pull the card out and try plugging the monitor straight into the integrated graphics—see if you can get any life out of it there.

Sent from my ASUS_Z00AD via Reddit

And here’s where I run into a bit of a snag. From what I can tell, I don't actually have any integrated graphics available to me, since all my monitor outputs are tied directly to my dedicated graphics card.
View on imgur

Is there any chance you could just borrow a GPU from another rig? Or maybe just pop yours into a different PC entirely to see if it actually works...

Yeah, totally, I'll give my old graphics card a shot once I get back home.