HELP: no extensions to call, while dialstatus=busy

I met a problem with my asterisk@home box:

when I give a call to an unregistered iax extension, I got the wrong announcement " the extion you are dialing is busy now". Both call from Pstn or from interal, will get the same result.

I guess the dialstatus is set to busy instead of chanunavail.

What can I do to solve the problem.

Thanks for your help.

Jeff zhu