Uhhh, I found it.The problem is this condemned PLCC socket. The emulator POD always got contact (maybe because of the longer pins) but the micro was missing contact at least at one of the pins. As I checked the resistance between the micro and the socket everything seems ok. Thank you, Mr. Murphy!

I bended all the socket contacts a bit an it's working. I never saw such flabby contacts in a socket.

Thanks for your help guys !