I suspected an automatic upgrade to 4.2.8.5 caused 2 system crashes (1 BSOD and one frozen black screen). Loading a week old restore point put me at 4.2.8.4 and so far so good. I've disabled automatic updates for now.
Also, enabling hardware acceleration on my Win 7 64 bit 16 gig i7 3770 w/GTX970 with the on-board graphics enabled causes my two Axis P3364VE cams to drop out. CPU usage is only 18% w/2x 2MP and 2x 1.3MP cams currently anyway though so no biggie. Jumps to about 28% when all 4 are recording D2D.
My h264 cameras dropped out with hardware acceleration on. (win7 64bit) I left hardware acceleration on & disabled run as a service & just leave BI running with the main window minimized. Works for now on version 4.2.8.4 this way.