3 weeks ago my hard drive failed so I bought a new one. (Macbook pro late 2011) 5 days ago, the new one flashed prohibitory sign, flashing folder with question mark. Every once in a while I could get it to desktop, but I would reboot, and back into the error. I reinstalled the OS through a USB, but still get the error. Is there a good chance it's the sata cable that needs to be replaced?
Flashing folder with question mark means that your mac can not find OS to boot. It's either it can not find some files needed in the early stages of boot up process, or can't find boot volume, or can't find the hard drive.
Before destroying all your data try reassigning your boot partition in Startup Disk preferences.
If that doesn't help check your cables. You simply might have not plugged them in firmly enough or there might be some dust in there that prevents good connection.
Check an article on the Apple KB for more options: A flashing question mark appears when you start your Mac.
First, you need to isolate the problem. Put the internal hardrive in a casing and connect it to your laptop through USB. Then boot up the OS X in this configuration by holding down OPTION key. If everything is smooth after a couple of hours, the problem is definitely SATA cable.
I have a 2011 13' MBP (A1278) and the cable broke a year ago. From what I read, the cable from this year (Parts No. 821-1226-A) is particularly faulty. You can replace it with the next iteration (821-1480-A). The latter is wider and longer, but it fits into older machines.