Perhaps I am wrong, but I think our personal ethics is what would be the driving force behind our professional ethics. Now, we might work harder to build our professional life than we do our personal life-such as a workaholic. However, ethics are a value system, and we must first have personal values before we can establish situational values.
I think that people can maintain professional ethics and fall short in personal ethics up to a point. I feel that eventually your "true" ethics will catch up with you and you will have problems remaining ethical in the professional world also.
Personally, I do not see why not. Professional ethics and personal ethics are very different things, after all.
Take, for example, Tiger Woods. In his golf career, no one has ever accused him of doing anything professionally unethical. But then we find out that he was doing things that were amazingly unethical in his personal life. I suppose that you could say the same thing about Elliot Spitzer.
I would think there are a lot of people who can be ethical in their professional lives because it is personal vices that are much more tempting than professional ones (I think).