Car does not start, anti-theft light blinks

I need some guidance on the tests to run to diagnose. Here are some facts:

1. The key fob works to open the car doors - I believe this is the original key fob from Ford.
2. When I put the key in the ignition, the lights on the dash light up, I turn the key - nothing!
3. I reinsert the key and no lights show up - except the anti-theft security light is blinking. At this point, I have no power, I cannot roll up the windows, etc.
4. The car does not crank at all - nothing happens.
5. I have tried to put the key in the ignition, wait 10-15 minutes with it turned and nothing.
6. I have tested the battery - the battery is good.

If I do the following:
1. Disconnect the battery, wait a few minutes, then re-attach.
2. Put the key in the ignition, I am able to roll up the windows, lights go on the dash, but no crank. Then I go back to the no lights on dash and anti-theft security light continues to blink.

Any ideas on what to do next?

Thank you,
Sharyn