Almost the same problem after update 1803 for Windows 10 and after installing 18.4.1 of the driver. Some games like Dragon Age: Inquisition hangs and freezes the system, but I can unfreeze it by putting the computer to sleep and waking it up (this tells me that the system is not completely crashed). Going back to 18.2.1 version fixed the problem while waiting for a new driver.
I forgot to mention this happens on a R9 290X.
Maybe make sure you system is set to "High Performance"
Disable Hybrid sleep.
This may help.