The diag light blinking six times can mean several things, but the only one that should occur with a "modern" modified firmware and distribution is an actual bad hard drive. If you remove the drive from the kurobox and can access it in another linux box then your most likely problem is a forced fsck taking longer than the kuroevtd allows before it times out and determines the hard drive is bad, triggering the 6 blinks on diag. It's been a few years since I encountered that problem, but the thread can be found here.
The other thread I linked to might contain more useful information as well. In short the solution is to simply fsck the drive in another system and put it back in the kurobox. That resets the fsck counter/timer and allows the kuroevtd to successfully complete the boot process.
BTW - I strongly recommend upgrading your kurobox to a newer firmware, one of many things it fixes is the forced fsck timeout.