Xuras

Certificates seem to be having a issue with the mumble server and requires you to change your clock back to last year this is seemly a bug in the past versions so make sure you always have the latest mumble client if you are having this problem! (link on the left)


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IMPORTANT: Update to Mumble 1.2.3a
Posted on January 15, 2012 by .D0T
Due to an expiring certificate no Mumble 1.2.2 or newer released before today (15.01.2012) will work on the Windows Platform after 15 January 2012 11:36:47 GMT. If such an outdated Mumble is launched after that date the error message “A referral was returned by the server” will be displayed by Windows and Mumble will not start.

You can get the fixed Mumble 1.2.3a stable installer from:
http://mumble.info/fix/mumble-1.2.3a.msi (uninstall 1.2.3 stable first).
An updated installer for the snapshot version is available from: http://mumble.info/snapshot/mumble-1.2.3-271-gca8b25c.msi
You can also download a fixed Mumble.exe for the 1.2.3 stable from: http://mumble.info/fix/mumble-1.2.3-resigned-binary.zip .

We are sorry for the inconvenience this may cause. We will follow up with a more detailed explanation later.

Regards,
The Mumble team
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Source: http://blog.mumble.info/important-update-to-mumble-1-2-3a/