Hello mitzirocker, I've to admit I've never heard of this problem before.
Could you please try the following steps:
- Verify the game files in Uplay (https://support.ubi.com/en-US/Faqs/0...s-In-Uplay-UPC)
- Make sure your graphics driver is up to date
- disable any background programs you might have active
How did you set up the graphics-settings in-game? Does your PC meet the minimum requirements for the game?