Problema bruiare

Salut , imi timp ce ma joc League of Legends sau alte jocuri (mai des la jocul asta) imi apare pe fractiune de secunda niste linii sau bruiaza ecranul... Am fost la service si mi-o testat tot pc iar placa video mi-o testat-o de 2 ori timp de 2 zile. De la ce ar putea fi? La monitor am cablu HDMI . Va spun si specificatiile pc-ului:
Primary OS: Windows 8.1 Pro
Motherboard: ASUS A88X-Plus
Case: RAIDMAX Viper black
CPU: AMD A8-6500 3.5GHZ , turbo mode 4.1GHz
GPU: Sapphire AMD Radeon R9 280X OC VAPOR-X, 3072MB, GDDR5, 384bit, HDMI, 2x DVI, Display Port
Power supply: nJoy 600RGE 600W
RAM: HyperX Fury Blue 8GB DDR3 1600 MHz CL10 Dual Channel Kit
SSD: Flash SSD Kingston V300 2.5", 120GB, SATA 3
HDD: WD Caviar Black 1TB SATA3 64MB 7200rpm
WD Green 500GB, 5400rpm, 64MB, SATA 3
Sound Card: Realtek High Definition Audio
Monitor: Monitor LED BenQ Gaming RTS RL2455HM 24 inch 1 ms GTG black-red
Keyboard: Gaming Natec Genesis RX22
Mouse: Genius X-G500
Mousepad: A4Tech X7 MP-200
Primary OS: Windows 8.1 Pro
Motherboard: ASUS A88X-Plus
Case: RAIDMAX Viper black
CPU: AMD A8-6500 3.5GHZ , turbo mode 4.1GHz
GPU: Sapphire AMD Radeon R9 280X OC VAPOR-X, 3072MB, GDDR5, 384bit, HDMI, 2x DVI, Display Port
Power supply: nJoy 600RGE 600W
RAM: HyperX Fury Blue 8GB DDR3 1600 MHz CL10 Dual Channel Kit
SSD: Flash SSD Kingston V300 2.5", 120GB, SATA 3
HDD: WD Caviar Black 1TB SATA3 64MB 7200rpm
WD Green 500GB, 5400rpm, 64MB, SATA 3
Sound Card: Realtek High Definition Audio
Monitor: Monitor LED BenQ Gaming RTS RL2455HM 24 inch 1 ms GTG black-red
Keyboard: Gaming Natec Genesis RX22
Mouse: Genius X-G500
Mousepad: A4Tech X7 MP-200