Asterisk freezes with Fixup failed on channel


i’ve got a recent problem which appears without any new modification.

I’m running asterisk on Fedora Core 2.

Since a few days, i’ve got a freeze in asterisk blocking everything (no new call possible, incoming or outgoing) even though the server is still up. (i can connect to the console, see peers connected, …)

Althought, on the phone, i’ve got “NR” (SNOM 3x0 phones) and nothing works

The error i’ve got previous of this freeze is the following :

WARNING[28008] channel.c: Fixup failed on channel SIP/8112-097c3a40, strange things may happen.
WARNING[28008] channel.c: Hangup failed! Strange things may happen!
WARNING[28008] channel.c: Failed to perform masquerade

the only solution is to kill the asterisk process (the “stop now” command does not work)

What is the cause of this problem, a bug in asterisk or a problem with one of the connected phone ?
is there a solution to this problem ?