TN-H1B-TN-again-H1B

I am Canadian. I got job in USA from March 2006 to September 2007, worked on TN Visa.
Oct 2007 I transferred on H1B visa. But H1B visa is valid still Sep 2011. But I am going to layoff from my company.
I am in touch with one of an other company. I have TWO questions:

1. If I start my new job on TN visa then my H1B will be expire or it will be valid till Sep2011 any case.

2. Say if my H1B will be expire in above case 1, then can after one year can I retain my H1B with my pay stub on TN visa?

Please reply me in detail.

Thanks,

I believe that if your employment ceases with the sponsor of your H1B visa, it becomes null and void, no matter what the expiration date is. Any subsequent employment must be sponsored by your new employer and with a new visa.

You can't hold two categories simultaneously, as soon as you get the TN-1 the H-1B is invalid, the expiry date is irrelevant. In fact it's invalid as soon as your old employer notifies USCIS you've been laid off. If your new employer files an I-129 for you, there is a 90-day grace period while the application is adjudicated, however that's not really relevant in this case because you're going from H-1B to TN-1, not H-1B to H-1B.

Back in 2003, I was on H1B with my previous employer which had more than 2 yrs left on it but I found another job. I took two weeks off and went back to Vancouver. I was granted the TN-1 at the airport when I flew down for the new job.