That's one crazy looking bug! I've not heard of this happening before so without more details I won't be able to recreate it and fix it. Please could I ask for the following information from you?
- Operating system? Are you on a 32 or 64 bit version?
- How much RAM/memory do you have?
- What graphics card do you have?
- What screen resolution are you using?
- Perhaps most importantly, which build/version of the game is this?