1. Check the RAM settings and timings and see if they match what's on the box.....do NOT turn voltage down to 1.50 if your RAM requires 1.65 volts. Again, check the packaging / specs, loads of SB compatible RAM uses 1.5 volts at 1333 speeds but needs 1.65 at 1600.
Sandy Bridge does not demand only 1.5v modules, it will be perfectly happy with 1.65v modules too. If someone tries to tell you that you must have 1.5v modules, then they are either trying to sell them to you, or they have been reading misinformation, or both! Another point to consider here, is that in your BIOS, if you head to the memory voltage setting, and enter 1.5v, the text will remain white/grey, if you enter 1.65v, it will turn yellow, and it isn't until 1.73v that it turns red, so at the moment, I'd rest assured that 1.65v modules are OK to use, and I have had this confirmed by Asus, Gigabyte and Corsair so far, as soon as I hear from anyone else, I will update this again.
The Asus MoBo manual for the P8Z68-V says:
According to Intel CPU spec, DIMM voltage below 1.65 is recommended to protect the CPU.
16GB Corsair Vengeance LP
2 sticks or 4 ?
If 4, try with just two memory sticks, in slots A2 and B2 (2nd and 4th from CPU)
Run memtest86+ overnight
Rinse and repeat with other two modules
If all pass, but fail with 4 modules in, you probably have to relax timings.
3. Do you have a means of monitoring voltages ? The HX series is an excellent line, but the 1000 and 1050 have had ripple and voltage stability "issues".
run the wd tools and smart tools for hard drive check that there no real errors. you may be having a drive that not spinning up or there a controller issue. next time the system hangs see if the drive is spining.