Does this happen a lot? Am I just dumb?

Bought/installed:

• M5A78L-M LX motherboard
• AMD Sempron 145
• EVGA 1300 PSU
• 2- Sapphire R9-280x GPUs
• 1 Dimm 4GB 1333 RAM
• installed LTCRabbit

It all finally showed up, I plugged in my one GPU that would fit directly into the mobo and it worked gloriously.

Bought: 2 Risers

They showed up and I plugged them in, things were working great for about a day. Then, LTCRabbit's web portal started acting funny. Files were missing or it was complaining about an error. No worries, restart!

No restart. BIOS Segmentation. No worries, Flash the BIOS!? Nope. Can't read USB drive on boot anymore, despite having power.

RMA the mobo. Go to local store, buy ASROCK 970 Extreme 4 mobo. Take it home, plug everything in... no power to USB on boot. Can't get into BIOS without a hard drive and PS2 keyboard.

Take the motherboard back, get new M5A78L-M LX motherboard.

Plug everything in. BIOS Segmentation. Won't read USB key, ASUS gives me an RMA and I take it back to local store.

Get M5A97LE R2 motherboard. Plug in one GPU, PSU, RAM, CPU. Boot. Fans spin, no power to USB, no visual coming from screen. So, here I sit with this motherboard trying to figure out wtf I'm supposed to do.

Please help me. I am lost, confused, it's cold outside, and I have sunk days of troubleshooting and about $1500 into this rig that is just collecting dust on my shelf.

UPDATE: My Dimm of RAM was bad. Apparently, it went to shit. We replaced it and everything booted right up.