PC freezing and USB turns off

[slashragnarok]

Okay so, since last night I'm facing a problem with my PC.

CPU: i5 2500k
Mobo: ASUS P8Z68 V Pro
RAM: GSkill Ripjaws 4 GB x 2 1600 MHz
GPU: Zotac GTX 960 Amp! (2 months old)
USB keyboard mouse
PSU: Corsair TX850 V2
Windows 7 Ultimate Edition

No overclocks

Everything's working fine till I find that my USB devices have lost power. This includes my keyboard, mouse, USB audio card and XBox 360 controller. Sometimes these devices are totally turned off, i.e. lights off. Sometimes one or two devices have their LEDs on but they are not responding. Disconnecting and reconnecting devices turns their LEDs off.

Moreover, the video card sends signal to the monitor but the screen freezes when the above happens. One time the PC was being shutdown and Windows was installing updates. The PC froze mid update. The only solution is to hard reset the PC. This freeze may happen after 30 minutes, or even a minute after startup.

One last detail is there was lightning in my area last night.

Any ideas? Thanks

 

[slashragnarok]

Okay just to add here. Basically what I did next was pull apart my PC and reassemble it. I posted this issue in July 2015. No issue till the first half of 2017. Now since the last 3 months, same problem. I'm thinking maybe the motherboard is getting short circuited somewhere. gonna try that again. A hassle given I have a huge heatsink and all but let's see.

03/09/17: UPDATE: Today after logging in Windows threw up a memory management error and restarted. I'm starting to think it could be a RAM issue. I remember now that 2 years ago when I first faced this issue, I ran Memcheck (Memtest??) and it did throw up an error. However I ran it several times after that and it did not come up with any. So I dismissed it as a one off event.

05/10/17: UPDATE: Okay so it was kind of a RAM issue. After giving up on the issue I just happened to open up the BIOS one day and the RAM voltage caught my eye. It read 1.675 V (bumped up by BIOS on auto) as against the rated 1.5V. So I set the voltage at 1.5 V manually and saw that the BIOS kept bumping up the voltage to 1.52V. So i set it at 1.4875 V and now the BIOS sets it at 1.5 V. Since then the problem appears to have disappeared *fingers crossed*