iTunes 12.1 - Pop and static when playing music

I've just upgraded to the latest version of iTunes (12.1.0.71) for Windows -- the first proper 64-bit edition of the software for Windows -- and now all my music has pops and clicks and other static when playing.

I have an extremely well-specced machine.

• Intel Core i7


• NVIDIA GeForce GTX 760


• 16GB RAM


• Windows 8.1 64-bit

Latest drivers. I even ensured I reset my machine after the installation.

What's going on? Every other music player on my system plays the same files perfectly fine.