Try this http://www.cisco.com/en/US/products/sw/secursw/ps2133/products_user_guide_book09186a00801071c8.html, think he must have missed the html

Better check the following bug before configuring,CSCea72383 - PIX crashes with isakmp nat-traversal command

You must be talking about the identification field, which generates a unique value for each session. I don't think its fixed for each type of traffic.

I also had a similair problem, I was using a steel belt radius. I changed the ACS radius flag and it worked for me.

It is passing the AP authentication thats why its associating in the first place.Check if the RADIUS server port is set to 1645. Try setting a WEP key in AP config to start LEAP if you have already not done so.