DSL loses signal during VOIP call.

I have had Verizon DSL via dry loop (DSL only...no POTS) for two years now at 768k down 128k up. I have a westell 6100 modem set up in bridge mode with my Linksys Router BEFSR41 doing the PPPoE authentication for me. Connected to the Router was my Linksys ATA phone adapter for my Verizon VOIP service. I have a wireless router connected to the wired too for wireless access. (WRT54G) They all worked great...until Verizon has now ended their VOIP service and I changed to another provider. I had verizon increase my bandwidth to 1.5 Mb down 384k up at the same time I changed VOIP providers though. That makes isolating the issue tough. What happens is that when I am on a VOIP call (incoming or outgoing) after a period of time (can be 1 min or 20 min) My DSL will lose signal and my whole network is gone. If I stay on the phone long enough the dsl wil re sync and I will resume the call. I have called Verizon and have gotten to level 3 tech support and they have sent a tech to test the lines and all is fone. I have ran my onwn speed and link quality tests from home and all is fine too. To eliminate the VOIP provider as being the issue, I cancelled the one I was with (Phone Power) and now have Vonage. The same thing occurrs. Is it the DSL, the cordless phone, the wireless router??? I am so frustrated. Verizon replaced the DSL modem and say the line is fine. The lowered me back down to 768k down and 128 up as I had no issues at that speed to see if that helps. I also have the phone adapter set statically, ports forwarded in my router and the adapter in the dmz. I will await any suggestions. Thanks all...