I've got an easily reproducable problem with call waiting on a WRP400. Here's the scenario:
A (voip user) calls B (WRP400). B answers and establishes a call.
C (voip user) calls B. Call waiting notifies B of the call. B hangs up with A and takes the call with C.
Within 30 seconds, the call between B and C will terminate. Debug logs on the WRP400 indicate the call is cleaned up, but no BYE is sent.
When C gives up and sends a BYE, the WRP400 will respond 481 Transcation Does Not Exist.
This is using the 1.01.00 firmware. I defaulted the WRP400 and entered just a proxy, username and password and still had the problem.
Now here's the weird part. I rolled back to the 1.00.06 firmware and the problem has gone away. That seems to indicate it's a bug in the 1.01.00 firmware.
Ever heard of such a thing?