I have the same issue: How to get IAS to work with m0n0wall.  I followed those exact instructions
and it did not work for me. (highly probably that i am too stupid to understand this as im totally
new to radius servers).

When i try to login through captive portal Something is happening on my IAS server cause when i
check the log i see connection attempts with the username and m0n0wall's information but i have
never been able to get through.

I thought perhaps im using the wrong format for my login names, I tried the following: username,
username@domain, username.domain.  none worked.

If i get some free time this week im going to reinstall IAS to be sure i didnt mess with too many
settings before attempting again.