I only started playing for the first time yesterday, but I have the same restrictions on my options. I am running 64-bit Windows 8.1 so it can’t be the lock on 32bit systems.
It’s probably unrelated but after some extended play my fps rate – 20-40 depending on where I was looking in the Grove – went to 10 and below, the game stopped playing sound and when I tried to quit it froze on a partially loaded character select screen. Had to soft reset my laptop as I couldn’t even work task manager, but could close other things (skype, chrome). EDIT: It worked perfectly after I restarted, framerate went back to being quite smooth, sound was back.
Doubt they’re related but others seem to have had framerate issues and this bug lately.