For anyone coming across this:

XP compatibility mode blocks any input occurring outside of the Juiced window, preventing LiveSplit from working properly. Turning compatibility mode off and using GrimMaple's JuicedFixes to avoid the virtual memory error fixed this issue.

Will do, thank you for the info!

I'm currently running the HD version on a HDD, but I have a spare SSD on hand, and I want to know if it's worth switching to. About how much time would I save if I did so? Does it have any noticeable effect on lag?