Problems with mail server certificates

Hi,

i have problems accessing my mail server over ssl since I upgraded from Lion to Mountain Lion.

The problem is, that when i try to connect to my mail server Mail stops working (and so does Safari and Keychain access).

I tryed to add my servers certificate to Keychain manually. When i drag the certificate to Keychain it shows up in Certificates, but when i try to set 'Allways trust' the application stops responding (and after that Mail won't send or receive anything and Safari wont load anythin until i restart the Mac).

Firefox is working without problems (webmail access which uses same certificate), even when Safari and Mail stop working.

Any idea what to do?