CPU usage drop and framerate drop

Hey there,

I installed Mass Effect 3 yesterday, after playing ME1 and ME2 without problems. However, I ran into a crippling problem: Every 5-20 seconds, the game hangs for about 2-4 seconds, having the framerate drop from 60 (with VSync, 100-300 without) to 0. Upon trying to find a solution, I noticed that the CPU usage of Mass Effect 3 (as seen in Task Manager and its Resource Monitor) drops to 0-3% every time these hangs/framerate drops happen. These drops happen anywhere in the game, from the main menu through the character screen to the gameplay. Even cinematics or the Esc menu are not spared. The severity of the framerate & cpu usage drops does not differ at all, regardless of whether it's in the middle of some effect-rich combat or any simple menu.

My system should be able to run this game without any problems, and the first 2 games (and every other game) ran flawlessly as expected.

Specs:

OS: Windows 7 Professional SP1 64-bit

CPU: Intel i5-4690K 3.5GHz Quad-Core

Graphics Card: MSI Radeon R9 390 8G

RAM: 16 GB (2x8) Kingston Beast DDR3-1600

Motherboard: Gigabyte GA-Z97-HD3

OS Hard Drive: Samsung 850 Pro SSD (256 GB)

External HDD: Western Digital 500GB wd50 00aads-00s9b0
PSU: EVGA 750W 80+ Bronze Certified Semi-Modular ATX

Nothing overclocked.

I'd be happy if anyone could help, this issue is making ME3 completely unenjoyable. ☹️

Edit: I also don't have any ASUS or ROG programs at all (custom built computer without bloatware), so they can't be the cause and disabling them is impossible.

Edit 2: Graphics card never exceeds 65°C and processor cores are all in 40-55°C range, 40-45 if idle. Idk if this is useful information but I figured I'd add it.