Huge ammount of GPU Memory Errors. Blank screen. Single tone. PC not responsive

[Hitman]

I have a problem with my PC. While playing, it crashes: screen goes blank, a single tone plays, i can only hard rest.
Using HWInfo (great app, btw ) i logged the status every second and found that there is a huge number of GPU errors in the last 1-2 rows of the log. The number is in the order of millions). What should I look at? 
I have a brand new GIGABYTE Radeon™ RX 480 G1 Gaming, 8GB GDDR5, 256-bit, but i got a similar crash on my old ati radeon

 

[Martin]

You should try to reduce the GPU Memory Clock to eliminate memory errors.

 

[Hitman]

You should try to reduce the GPU Memory Clock to eliminate memory errors.

Thank you for your reply. Looks like that did it.