I just bought a new computer:
Windows 7 Home Premium 64bit (6.1, Build 7601)
Intel(R) Core(TM) i5-4670K CPU @ 3.40GHz
Sharkoon WPM500 V2 500
Gigabyte GA-Z87-HD3 Z87 RG SA
Seagate ST2000DM001 2 TB
SSD 120GB 410/540 840 EVOBasic SA3 SAM
I mostly play Guild Wars 2, on high settings and the game runs smoothly on 60 fps (limited on 60). But sometimes the game gets all laggy, my frame rate drops and it is unplayable, even on low settings. My gpu works at 100% activity when that is the case. I have tested multiple things: other settings, re-install of the drivers and playing on lower settings, gpu benchmarks (also laggy when the game lags) but nothing seems to work.
Also other games get laggy when this happens. It seems to happen at random and will most of the time not get fixed when i reboot. The funny thing is, I can game for hours without anything happening. But some days when I start up my computer the lag is there already.