I have this problem:

[Nov 9 12:59:55] WARNING[15055]: app.c:1048 ast_lock_path: Failed to lock path ‘/var/spool/asterisk/voicemail/mb_voicemail/2223/INBOX’: File exists
[Nov 9 12:59:55] ERROR[15055]: app_voicemail.c:4395 leave_voicemail: Couldn’t lock directory /var/spool/asterisk/voicemail/mb_voicemail/2223/INBOX. Voicemail will be lost.
Anybody know how fixed this problem???

Check the user rights for /var/spool/asterisk/voicemail/. Asterisk needs to have RWX rights to save the Voicemail files.