Got a weird message saying the system was low on memory. Pulled up task manager and the game was using roughly 14gb of RAM! System only has 16gb. First time it's happened, but I've never seen anything do that before. Hopefully there isn't a memory leak or something.

I had the same problem and just restarted the game as you said.

would you mind posting what kind of hardware you are using (OS, CPU, GPU, Witcher Graphic Settings?)
I didnt have any issues yet despite only having 8 GB of RAM - i gonna check more extensively where my ram usuage is after a hours of gameplay this afternoon.

I have the same issue, game starts at around 6gb and in about an hour goes to 14k gb

my specs are:

Win 7 64bit
AMD FX 8320 @4.3ghz
MSI 390 @1100/1600mhz
Corsair Vengeance 16gb

I have the latest drivers and the game settings are on high, except the nvidia settings which are off

Win7 Ultimate
MSI GTX 970
FX 8350
16gb Rip Jaw
1000w EVGA

Settings are Ultra for textures, etc.
Shadows medium
HBAO+
No Fish eye
Hairworks Ultra preset but NO AA
Game AA on
Border less full screen
V-sync OFF but FPS capped at 60

It's getting roughly 3gb an hour. Any longer and it might as well be a RAM stress test. If it's starting at 6gb, that's pretty serious.