Okay, so I'm having the dreaded grey screen on my iMac - precisely :
- i'm having it doing a normal startup
- i'm having it trying to boot from recovery partition
- i'm having it trying to boot for internet recovery
- i'm having it trying to boot in safe mode
- verbose mode is no help because it ends with a grey screen before I've time to read anything
- i have a windows partition which also fails to boot, except in safe mode - from where I can access all my HD partitions without any error by the way
- fsck -fy in single user mode reveal no volume error
- an extended Apple Hardware Test reveal no hardware error whatsoever
- replacing RAM modules didn't change anything
So I'm stuck : what can possibly cause the problem if it is neither the OS (remember I'm having trouble with both MacOSX and Windows), and nor the hardware (at least if AHT is indeed reliable) ? I thought a driver might be involved, but I haven't upgraded or changed any driver on my machine since ages ago, and it worked perfectly fine until last sunday.
If anyone has an idea, please help, because I can't even point out support with a possible cause for failure here.