Sony PCG-F390 - Manual (Page 75)

Troubleshooting 65
Power Management
The operating system may become unstable if a lower power state such as
system hibernation is initiated and then changed before the operating
system completely enters the lower power state. To restore the computer
to its normal operating stability, close all open applications, press the
power button, and hold it for four seconds or more to completely shut
down the computer.