As this has been bothering some of us for a while, I thought I would share an informational post. For those us you who, after upgrading to Slackware 14, suddenly had mumble "go robotic" with some, but not all, remote clients, go to
http://www.slackbuilds.org and grab/install the updated mumble package. This slackbuld now uses the bundled celt-0.11.0. The SBo system-wide package is celt-0.11.3. According to Xiph.org, versions can not me mixed and matched.
Of course, I fixed this on my end at 1 am last night and
then discovered the updated slackbuild when I was creating a diff patch to post here. Oh, well...
The issue was the version of Celt. Windows users install the precompiled package linked to celt-0.11.0, as are some linux distro repositories. As a result, any OS that installed mumble linked to a newer, system-wide celt, will have problems talking to those linked to the bundled celt.
Conclusion: Use the bundled celt-0.11.0 that ships with mumble-1.2.3.
I haven't noticed any mentions of this on LQ or on the SBo mailing list and there are still numerous forum posts around teh web that dance around this issue with no result. Hopefully, this helps anyone who is still banging their head aginst the wall!