Description of problem:
when gnome-shell start an error occurring and close the session.
The error message it is:
Window manager warning: Log level 16: gsignal.c:2295: signal `app-state-changed' is invalid for instance `0x1d4bca0'
Window manager warning: Log level 16: Failed to load shared library 'libcaribou' referenced by the typelib: libcaribso.so: cannot open shared object file: No such file or directory
Window manager warning: Log level 8: g_ascii_strncasecmp: assertion `s2 != NULL' failed
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libcaribso.so ?? maybe they are a typo problem somewhere, me i expect see 
libcaribou.so