metacity freezes when swithching to another virtual desktops

[salva]

When I switch from one virtual desktop to another using the keyboard (i.e. ctrl-alt-left), sometimes it freezes and the X become completely irresponsive. I have to go to the console and kill metacity in order to recover it.

This is the backtrace I get if I attach to the metacity process once it hangs:

#0 pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:144
#1 0x00007f0d35227180 in pa_threaded_mainloop_wait () from /usr/lib/x86_64-linux-gnu/libpulse.so.0
#2 0x00007f0d3546c732 in pulse_driver_play () from /usr/lib/x86_64-linux-gnu/libcanberra-0.30/libcanberra-pulse.so
#3 0x00007f0d3fe1a98e in ca_context_play_full () from /usr/lib/x86_64-linux-gnu/libcanberra.so.0
#4 0x00007f0d3fe1ad0f in ca_context_play () from /usr/lib/x86_64-linux-gnu/libcanberra.so.0
#5 0x0000000000445532 in ?? ()
#6 0x0000000000429c68 in ?? ()
#7 0x000000000042ab22 in ?? ()
#8 0x000000000041f54e in ?? ()
#9 0x0000000000460044 in ?? ()
#10 0x00007f0d3f586576 in ?? () from /usr/lib/x86_64-linux-gnu/libgdk-x11-2.0.so.0
#11 0x00007f0d3f587ca8 in ?? () from /usr/lib/x86_64-linux-gnu/libgdk-x11-2.0.so.0
#12 0x00007f0d3f587d4e in ?? () from /usr/lib/x86_64-linux-gnu/libgdk-x11-2.0.so.0
#13 0x00007f0d3d519a95 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#14 0x00007f0d3d519dc8 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#15 0x00007f0d3d51a1c2 in g_main_loop_run () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#16 0x000000000040facd in ?? ()
#17 0x00007f0d3be95c15 in __libc_start_main (main=0x40f250, argc=1, ubp_av=0x7fff683e1f28, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff683e1f18) at libc-start.c:227
#18 0x000000000040fe99 in ?? ()

(BTW, is there any package containing the debugging symbols for metacity?)

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: metacity 1:2.34.13-0ubuntu1
ProcVersionSignature: Ubuntu 3.7.0-4.12-generic 3.7.0-rc7
Uname: Linux 3.7.0-4-generic x86_64
ApportVersion: 2.7-0ubuntu2
Architecture: amd64
Date: Wed Dec 19 17:47:47 2012
MarkForUpload: True
SourcePackage: metacity
UpgradeStatus: Upgraded to raring on 2012-12-03 (15 days ago)