The percussion take on the source is very well executed. I took time to appreciate completely this track, but this is a very solid song from a very cool album. Nice work.
You should look for MIDI files. They actually contain the "original" notes and are very, very helpful. Check this website, I'm sure you'll find what you're looking for.
Castlevania: Lords of Shadow has a very different soundtrack from what the series is known for.
Also, Dante's Inferno. Hellish soundtrack, needs at least one remix.
Are you using FL Studio's extended memory version? If not, it may be the problem.
Also, it can be caused by the big usage of CPU/Sound card/something like this.