Thank you Diego_Intel,
your suggestion on restore point led me to believe solution lies somewhere within the driver changes. I checked IDE ATA/ATAPI controllers in device manager, and found out that my latest chipset driver update somehow overridden RST drivers and put its own instead. Driver details didn't show iastore.sys but it was something else. So I used -P -A to extract the RST drivers, and manually updated AHCI controller. Now everything works fine.