I've been trying to track down an issue ever since I bought my E3000. I have Vonage and the phone adapter is connected directly to the router. The only other connection to the router is the cable modem and my switch.
With the new router about 50% of my calls don't come through the phone, but instead fall over to my wife's cell phone. We have Vonage setup so that if the phone adapter is not working, then to have the calls forwarded to her cell phone. This part works fine.
I have never had an issue placing a call out with the router, just receiving them. Initially I thought it was related to some routing with the —tee option, but that is not the case.
Just to test that it was the router, I put my old wrt54gs back into service for a week and did not have one call forwarded to the cell phone.
Any ideas on what to look for? I just flashed to DDWRT, and now remember why I don't like it! I'll see if DDWRT works, but would really like to run tomato. I use dyndns and opendns and DDWRT has abysmal support for opendns.