I have never used GrandCentral. I had never even heard of it until I tried to look up the problem in Maemo bugzilla before reporting a new bug.

You are using Gizmo for your DTMF. I imagine it does work fine in that, as that is not the application being referred to. I use a standard SIP provider. I like the SipPhone service, but I don't like or use the Gizmo app. I need a standard VoIP app.

The problem referred to is a problem with the Maemo OSSO application "Internet Call." This application was made by Nokia Open Source Software Operations, which probably means it's closed-source. DTMF worked correctly in OS2007. DTMF does not work in OS2008 "Internet Call" after the call is initiated. Period.

I tried creating a new bug. The Maemo bug keepers, however, did not wish to acknowledge the bug. That is another reason why I hate all this Maemo business - it's hard to get decent support with proprietary software and such a small installed base. I doubt a bug of this type would go unresolved for a year with Debian. I wish Debian was a bit more usable in the tablet. . . at this point my only reasonable alternative is to try to install the Twinkle VoIP app in Debian, or ditch my tablet or use Skype. OTOH, if DTMF works in Gizmo for you then maybe that is another alternative I can try! Thank you for that idea!

Unfortunately, however, Gizmo only supports a single SIP account. There are other issues also with it which I do not like, but at least you can use your own SIP account, which you can't do with Skype.

Gizmo is only a workaound, however, the bug in "Internet Call" is still there. . .