I think I posted this problem before, because I had this issue before I changed my motherboard, but here goes:
I'll be updating this post as I do more test, but maybe someone can diagnose it with the information I have. I have an asus board, P7P55D-E PRO, and a OWC Mercury Elite Pro 6G SSD. It's been running fine for about 6 months now since I installed my new mother board. But now after I shut it down for the night and turn it on in the morning, after the BIOS splash screen it some up with "please insert proper boot media". Going into BIOS reveals that the hard drive is not there. This has happened for the past 3 days. Once I get it working again I can not replicate the problem. Only after it's shut off for the entire night does the problem recur.
This happened after a while on my previous mother board as well. I've tried many things to fix it, updating firmware on everything and changing settings. It always comes back on though... but I'm not exactly sure if any of my actions have any effect. I've tried opening up the case and unplugging and replugging the drive, but I think I had to restart it two more times after that before the drive was recognized. This last time I just kept restarting the computer until it came back on after 7 tries. Tomorrow I'm going to try booting it up, shutting it down, then just leaving it sit for 15 minutes and try again, see if I have any effect at all or if what I'm doing is just a ceremonial dance.
The problem really seems to be with the hard drive, considering a new mother board apparently didn't fix it (but it's weird that it takes 6 months to show up again). When it happened before I tried all sorts of different cables and that didn't seem to fix it either. If anyone has any suggestions other than "Get a new SSD" then let me know. More of my specs are spoilerd below.
OS Version: Microsoft Windows 7 Home Premium
System RAM: 16358 MB
CPU Name: Intel® Core™ i7-2600K CPU @ 3.40GHz
CPU Speeds: 4849
Physical CPUs: 1
Virtual CPUs: 4
Video Card Description: AMD Radeon HD 6800 Series
VRAM: 1024 MB
Primary Display Resolution: 1920x1080
Multi-Monitor Desktop Resolution: 1920x1080
Language: English (United States)
Free Hard Drive Space: 35808 MB
Total Hard Drive Space: 228833 MB
Windows Experience Index Rating: 7.7