Crash, horizontal red lines, won't boot, SMC PRAM reset, failed boots, successful boot cycles:
For about a week, I have been struggling with crashes, followed by red horizontal lines on the screen, and inability to boot into multi-user mode. It will boot into single user mode, with red stripes on black background. To get it to boot again I "shutdown -h now" from single user mode, SMC reset, PRAM reset 3 times, and attempt boots with <command> R two to three times unsuccessfully. Then, if I am lucky, when I do a boot into single-user mode (power, <command> S), it boots into single user mode with a black background and no stripes, then I "exit" to boot. If I am unlucky, the black screen will have red stripes or red snow in single-user mode. After several crashes, I also have to remove my hard drive, and do a disk repair and permission repair, while connected to a different mac, or format and restore ML. (I have two backups of my personal data.) The failed multi-user boots are terminated by grey or black screens of death, accompanied by heat and the fands running fast. The fans also run in single user mode without processor load if they red stripes are on the screen. A successful multi-user boot is cool without fans running. I didn't have any crashing problems before switching to ML recently.
Memtest fails in multi-user mode (but not single-user mode):
Running memtest on 8GB RAM in multi-user mode fails at a single address on the most significant byte (with 1 bit difference). However, memtest does not show a failure in single-user mode, nor with only a single 4GB module in multi-user mode.
Increased stability with gfxCardStatus and Flash unininstall:
Using gfxCardStatus Integrated Only mode, and uninstalling Flash, seems to help. However, I do get crashes or inability to wake up display which seems to be associated with processes like (google Chrome renderer) which forces gfxCardStatus out of "Integrated Only" mode. http://gfx.io/switching.html
I am in Mexico where RAM is outrageously expensive. So I will order RAM from the USA and try new 16 GB RAM because it is cheaper part swap than the logic board. It makes sense to try the cheap stuff first. I would rather switch to Linux and continue my bioinformatics work than pay and wait to replace the i7 logic board which warranty expired a few months ago. I refuse to hit it with a heatgun to reflow the BGA solder on the GPU. I really need the i7 data processing throughput I paid for.
Does anyone understand the ambiguous memtest results?