Set the bios to IDE.
Then try this Start Up repair.> Startup Repair
On your Acer you probably don't have disks but there should be an option/key for advanced menu. Read your manual or get manual download from Acer web site.
Then you can follow the tutorial once you find that option/screen.
F8 is often used on HP's but Acer I have no idea.
This is the only option I can think of at the moment that may work. It won't hurt anything.
I have an older acer aspire desktop and had an IDE/ACHI issue in that certain boot CDs required the BIOS IDE setting for sata devices to be recognized. Also windows would see the ata as scsi in device manager. So I ended up with BIOS set to IDE and the ACHI reg fix. Sata devices were then seen by Device Manager as ata.
AHCI : Enable in Windows 7 / Vista
HDD speeds were just as good and all software recognized the sata devices.
Why your situation should suddenly change is puzzling. The BIOS update is looking like an option worth considering.
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