Hello, I experienced exactly the same issue after renewing my licence by downloading Eset Nod32 ver 7 (former version on my computer was ver 4). My external hard hard drive unit is not recognized and causes my computer to freeze with no alternative but switching it off. Since I don't find any solution, I uninstalled ver 7 and installed ver 4 again. Since then, everything works fine.
I have upgraded from ver 4 to 7 on December 2, 2013. The problem is that my computer doesn't recognize my external hard drive anymore when the drive is switched on and freezes. I'm forced to reboot it. I uninstalled ver 7 and reinstated ver 4 and everything is ok now. Anyone experienced this issue?