How to I diagnose and repair "not booting" in an existing installation?

I installed Mint 17.1 on a fresh SSD, along with Clonzilla in another partition, and rEFInd in the EFI System partition (more details vide infra).

It worked on the bench, but now put together in the chassis with graphics cards installed it does not work.

I can kick it off via rEFInd, and the screen goes blank and nothing happens. Clonezilla does boot, though. I've removed other drives and peripherals so it's just like it was before when working, except for the graphics cards.

I believe that rEFInd starts the grub on that partition, but it doesn't pause to show a menu. There is probably some way to make that show up so I can choose the "safe mode" or "verbose mode" or whatever?

The installer that I had used (Live on USB flash drive) does boot.

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Linux Mint 17.1 Cinnamon x64, Supermicro X10SAT w/E3-1276v3, GeForce GTX 560 and GeForce GT 430.

I installed / to partition 2, /home on partition 4; told it that the / partition (not the drive as a whole) was the boot device; I booted with EFI choosing the partition until installing rEFInd.