Re: invisible errors
The Event Viewer may or may not help. Many times problems are accompanied by repeating errors that may describe the situation in a way that might help someone track it down. So in the Event Viewer, you go to the errors and see if anything is showing multiple instances of a problem and even check when they are occurring. If you double click the error, another page shows up that will give a two or three line description of what caused the error. The message may contain devices, or utilities or error codes that can be used.
If there are no errors that seem relevant, you might also check the warnings to see if anything there is showing up that could be related.
There have actually been a couple of times when I sent the info to Microsoft, they actually had a fix. I almost fell out of my chair! 
Glad you found the problem.
Operating System Win 7 x64
Computer Type Homebuilt
OS Service Pack 2
DirectX Version 11
CPU Type and Speed i7 3770K
Motherboard Chipset Asus P8Z77-V Pro
System Memory Type 16 GB Kingston
Video Card Type and Speed Nvidia GTX 680 (2)
Computer Monitor LG 27" (3)
Hard Drive Kingston 240 SSD
Optical Drives LG WH12LS30 Blu-
Modem-Router Type Linksys E3000
Network Adapter Intel Gigabit
Anti-virus Software MSE
Computer Skill Level Average Ability
Windows Experience Index 7.7