Brett,
There's a problem I recall from when the 4500s first shipped where the modems were especially sensitive to the voltage on the phone line. It was fixed in the 4.3, build 29 or later build of software. Once the unit actually upgraded to 4.3, build 29 or later it went away.
The problem didn't seem to affect all phone lines. Is there any way you could possible hook the unit up via Ethernet to get the latest software version? Or, test the unit at a different location?
Additionally, there are a couple things you can try to work around the problem that have some success. You can try removing all telephony devices from your phone line during setup. You can also try the following: Disconnect the phone line during setup. Let the unit get a no dial tone error. Then, reconnect the phone line. Once it's finished the first connection and has the list of local #s. Disconnect the phone line again until it tries to call the local # you picked. Then, reconnect the phone line and have it try again.
The pretty confident that the unit you have is running 4.3, build 26 which doesn't have the fix. Most likely, your orignal unit was running build 18 or 26.
Lyndon
