Things that seem to affect UMA include: brand or model of router, router OS, phone OS version, settings in the router, security protocol on the router. The only stable calling I get is running DD-WRT on a Linksys WRTGS router, and WPA security. In other places I can use UMA, but it's not reliable.
I try not to use UMA except for calls where I can call them back if the call drops, as in, not for more serious business calls. I have had calls over an hour before on UMA, so it can work out.
Things that I'd check are making sure the phone is on a newer OS. Avoid N routers -stick to plain G compatible, and see if you can set QOS settings in the router.
Last edited by monkeypaw : 07-24-2010 at 05:28 AM.