Selenium crashes Firefox, how to reset the used profile / where is the default profile?

Question

I have a test project which is powered by Cucumber, Selenium and Java

Problem: Firefox crashes when it is started by selenium, after i click on okay on that popup firefox runs normal. This problem is only on my maschine. On our integration server it runs just fine. I think my Firefox Profile is defect.

Question: Where is the profile which is used by selenium locate? I use windows by the way. And is there a way to reset it?

Infos: I instantiate the WebDriver like this:

FirefoxProfile ffProfile = new FirefoxProfile();
ffProfile.setAssumeUntrustedCertificateIssuer(false);
FirefoxDriver ff = new FirefoxDriver(ffProfile);

And i use the newest firefox

Thanks in advance, if further information is needed, just leave a comment and i will profide it if possible.