Laggy preview when scrolling through the timeline

Hi!

I have some performance issues with Hitfilm, and it happens when I use the Particle simulator. Even the stock 3D effects like the "Dragon's Breath" are choppy when playing and scrolling through. Trying to combine the simulator with movie clips makes it almost unusable.

I thought that maybe the system requirements where through the roof, but after checking it out my PC should be well over recommended.

My PC:

Windows 8 64 BIT, GTX 780 with 3 GB VRAM, 8 GB RAM, i7-2600k.

So is there anyone who's had similar issues and found a solution?