Macbook Pro Mid-2012 Disk I/O Error (One time) after SSD install

So here's the deal:

I have two Crucial SSDs, and I'm trying to set up my Macbook for dual internal hard drives. I already have them both in place, and the drive in the main drive bay has OS X installed and I'm actually currently using the computer to type this out.

For hours, the computer has run beautifully, like a charm. However, an hour ago I was on Skype, and the app abruptly exited, saying there was a disk i/o error. The entire OS froze, and I needed to shutdown the computer. I've run Disk Utility and verified the disk, and I even ran an Apple Hardware Test on the computer, though I doubt that would tell me if something like my SATA cable were faulty.

What really gets me is that I partitioned the drive in the main bay and have been reading and writing large amounts of data without any issue. In the past 6 hours, ~140 GBs of data has been written to this drive. No I/O errors--nothing.

Do you guys think this is a one-time thing? I have no clue, and I'm afraid that I'm going to go back to college, work on some long project, and then lose a lot of work because of some I/O error again. Could it be a slightly faulty SATA cable? Would it be worth replacing just in case? Or should I just wait it out and see if this issue crops up again?

Thanks!