Arduino IDE 1.6.6 won't start

Hi everyone!
My Arduino IDE 1.6.6 won't start. I know there are a lot of solutions already on the Internet, but none of them worked for me, that's why I am posting this.
So what happened was:
The IDE worked before, even 1.6.6
I tried the turning off bluetooth fix because it seemded to help many people with the same problem but it didn't work for me.
When I start the IDE, the little "loading" (?) screen pops up but normally when the real window should appear, it doesn't. The little screen saying "An open procet written by, debugged by..." and so on seems to freeze and the disappearing.
I also tried updating java to the latest version, but it did also not help.
Thanks for helping me out! It's really annoying not being able to do anything with my arduino...

Fred

Update: the problem was my computer, not the IDE.