linux telephony

It has been a sore point for me for a while that I haven't been able to get decent telephony on my linux desktop. I'm running Ubuntu 9.10 on an old HP two Xeon processor workstation. I'm working remotely, cell phone coverage it near non-existent at my house, my T-Mobile Blackberry doesn't seem to do a good job of staying connected to my wifi router, and I want to keep my home phone free (I spend about six hours a day on the phone for work).

From work, I have a windows laptop running XP SP3, I use a Cisco VPN to connect into the office, and have the choice of two Cisco softphones to use. Problem is, my laptop has a knack for hanging and bluescreening just before meetings. Like right now.

I have Google Voice. Ability to forward calls to Gizmo5 means I can do free SIP to PSTN. But I need to be able to do DTMF, for the various teleconferences I need to join. Skype doesn't do it. Gizmo5 doesn't seem to work with my audio setup. Ekiga screeches at me. Finally, when I log Twinkle into Gizmo5, I have happiness.