On Tue, 2012-02-21 at 10:58 +0100, postmaster wrote:
#0 0x90003afa in mach_msg_trap () No symbol table info available. #1 0x90004267 in mach_msg () No symbol table info available. #2 0x9001b431 in vproc_mig_look_up2 () No symbol table info available. #3 0x9001b26a in bootstrap_look_up2 () No symbol table info available. #4 0x9001b0e4 in bootstrap_look_up () No symbol table info available. #5 0x9001af30 in notify_register_check () No symbol table info available. #6 0x9001ada7 in notify_register_tz () No symbol table info available. #7 0x9001a621 in tzsetwall_basic () No symbol table info available. #8 0x90041903 in localtime () No symbol table info available.
All of the above functions are OSX's internal functions in libc.
#9 0x0007ba2f in mail_index_update_day_headers ()
So Dovecot calls localtime() and the process hangs. Something's badly broken in your system related to timezone handling, nothing Dovecot can do about it..