Why Does Testing mozilla-firebird Wants To Remove diald

[David Crane <davidcrane@mfire.com>]

When I try to "apt-get install mozilla-firebird" from the
testing distribution, it wants to remove the diald and ppp
packages.  I am certain that that would be bad, and that I
have done something wrong.

I added the following to my /etc/apt/sources.list:

dev http://http.us.debian.org/debian testing main contrib non-free

If the solution isn't obvious, please reply to the list with what other 
information I should gather.  I'm pretty new with
using debian, but I'm very experienced with writing UNIX
server software.  I'm impressed so far.

Thanks,
David Crane