asterisk users - Nov 2004 - Cisco 79XX - Using built-in 3way conference

Hey guys,
 This has worked before but for some reason isn't anymore and I have no clue
what to check.
Here are the steps I follow:

1. Place call to PSTN number. They answer and we talk.
2. I press 'Conference' button on Cisco phone.
3. Line 1 is now on hold and I get a new dial tone.
4. Place call 2 to another PSTN. They answer and we talk.
5. I press 'Join' on the Cisco phone. Caller 1 gets dropped and I get
the
following
message in * console:

  Got SIP response 481 "Call Leg/Transaction Does Not Exist" back from
10.0.0.122

Now, 10.0.0.122 is the IP of my Cisco phone. * has 2 NICs, 1 is 10.0.3.10
and the other is external public IP. I can make/recieve calls all day long.
But recently this conference stopped working.

Any ideas on what to check? The error doesn't make sense since the 2 calls
are present. Right before I press join, I can put caller 2 on hold and
resume caller 1 and vice versa. It isn't until I press 'Join' that
call 1 is
dropped.

This works fine if caller 1 and 2 are both other phones in the office or
caller 1 is a phone in office and 2 is PSTN. Just doesn't work when both
PSTN. Worked before..

THanks,
Matthew

Matthew Boehm wrote:
> This works fine if caller 1 and 2 are both other phones in the office or
> caller 1 is a phone in office and 2 is PSTN. Just doesn't work when
both
> PSTN. Worked before..
What codecs are involved? If you are using low-bandwidth codecs for PSTN 
connections, the Cisco phones will refuse to conference two 
low-bandwidth calls together. They may work with a ulaw and a 
low-bandwidth call, but I haven't tested that.