You should contact their support. Red Gate has an excellent support team and I'm sure they would be helpful in checking if their product is causing problems.
I'm currently running Windows 8.1 and SQL Management Studio 2012, and I haven't had any problems with Red Gate products, I've found that SQL Prompt is extremely fast and efficient.
Why is it that people who can't take advice always insist on giving it? - James Bond, Casino Royale