When i reenter the atmosphere of a planet the game freezes and won't react to any input.
I've been searching all over the web but i haven't found any answers.

I don't get a crash log.

This only happens when i have mecjeb on the ship or a debris.

Sorry for bad english.

This needs more information. What mods are you using if any? Try a fresh install of KSP with mechjeb 2 as the only mod (Back up your old gamefiles first). Does it still happen? If not, it's not KSP or mechjeb 2, or you may not have had the most up to date version.

If it still happens:
Are you running the latest versions of everything?
What operating system do you use?
What are your hardware specs?

Not much useful stuff here, so I'm going to close this issue.