Hallo,
den Fehler kann man, leider nur manchmal, reproduzieren:
Man öffnet Sunbird, klickt auf einen Termin (dann stürzt er ab. Funktioniert aber eher so alle 2-3 Tage einmal)

Ich habe mal Sunbird so gestartet (im Terminal):
strace sunbird
Es folgt dann folgende Fehlermeldung:

####### start Fehlermeldung ########

execve("/usr/bin/sunbird", ["sunbird"], [/* 36 vars */]) = 0
brk(0)                                  = 0x9bc6000
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
mmap2(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb8054000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=92743, ...}) = 0
mmap2(NULL, 92743, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb803d000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/tls/i686/cmov/libc.so.6", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\320h\1\0004\0\0\0\344"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1442180, ...}) = 0
mmap2(NULL, 1451632, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7eda000
mprotect(0xb8036000, 4096, PROT_NONE)   = 0
mmap2(0xb8037000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x15c) = 0xb8037000
mmap2(0xb803a000, 9840, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb803a000
close(3)                                = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7ed9000
set_thread_area({entry_number:-1 -> 6, base_addr:0xb7ed98d0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
open("/dev/urandom", O_RDONLY)          = 3
read(3, "\\\311\303l"..., 4)            = 4
close(3)                                = 0
mprotect(0xb8037000, 8192, PROT_READ)   = 0
mprotect(0x805d000, 4096, PROT_READ)    = 0
mprotect(0xb8073000, 4096, PROT_READ)   = 0
munmap(0xb803d000, 92743)               = 0
getpid()                                = 2459
rt_sigaction(SIGCHLD, {SIG_DFL}, {SIG_DFL}, 8) = 0
geteuid32()                             = 1000
brk(0)                                  = 0x9bc6000
brk(0x9be7000)                          = 0x9be7000
getppid()                               = 2458
stat64("/home/doni", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
stat64(".", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
open("/usr/bin/sunbird", O_RDONLY)      = 3
fcntl64(3, F_DUPFD, 10)                 = 10
close(3)                                = 0
fcntl64(10, F_SETFD, FD_CLOEXEC)        = 0
rt_sigaction(SIGINT, NULL, {SIG_DFL}, 8) = 0
rt_sigaction(SIGINT, {0x8056770, ~[RTMIN RT_1], 0}, NULL, 8) = 0
rt_sigaction(SIGQUIT, NULL, {SIG_DFL}, 8) = 0
rt_sigaction(SIGQUIT, {SIG_DFL}, NULL, 8) = 0
rt_sigaction(SIGTERM, NULL, {SIG_DFL}, 8) = 0
rt_sigaction(SIGTERM, {SIG_DFL}, NULL, 8) = 0
read(10, "#!/bin/sh\n#\n# ***** BEGIN LICENSE"..., 8192) = 7696
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7ed9918) = 2460
--- SIGCHLD (Child exited) @ 0 (0) ---
close(4)                                = 0
read(3, "/usr/bin\n"..., 128)           = 9
read(3, ""..., 128)                     = 0
close(3)                                = 0
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 2460
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7ed9918) = 2461
close(4)                                = 0
--- SIGCHLD (Child exited) @ 0 (0) ---
read(3, "sunbird\n"..., 128)            = 8
read(3, ""..., 128)                     = 0
close(3)                                = 0
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 2461
stat64("/usr/bin/run-mozilla.sh", 0xbf9732bc) = -1 ENOENT (No such file or directory)
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7ed9918) = 2462
close(4)                                = 0
read(3, "/home/doni\n"..., 128)         = 11
read(3, ""..., 128)                     = 0
close(3)                                = 0
--- SIGCHLD (Child exited) @ 0 (0) ---
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 2462
lstat64("/usr/bin/sunbird", {st_mode=S_IFLNK|0777, st_size=22, ...}) = 0
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7ed9918) = 2463
--- SIGCHLD (Child exited) @ 0 (0) ---
close(4)                                = 0
read(3, "sunbird\n"..., 128)            = 8
read(3, ""..., 128)                     = 0
close(3)                                = 0
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 2463
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7ed9918) = 2464
close(4)                                = 0
read(3, "/usr/bin\n"..., 128)           = 9
--- SIGCHLD (Child exited) @ 0 (0) ---
read(3, ""..., 128)                     = 0
close(3)                                = 0
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 2464
chdir("/usr/bin")                       = 0
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7ed9918) = 2465
close(4)                                = 0
read(3, "../lib/sunbird/sunbird\n"..., 128) = 23
read(3, ""..., 128)                     = 0
--- SIGCHLD (Child exited) @ 0 (0) ---
close(3)                                = 0
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 2465
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7ed9918) = 2468
--- SIGCHLD (Child exited) @ 0 (0) ---
close(4)                                = 0
read(3, "sunbird\n"..., 128)            = 8
read(3, ""..., 128)                     = 0
close(3)                                = 0
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 2468
stat64("../lib/sunbird/sunbird", {st_mode=S_IFREG|0755, st_size=7696, ...}) = 0
geteuid32()                             = 1000
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7ed9918) = 2469
close(4)                                = 0
--- SIGCHLD (Child exited) @ 0 (0) ---
read(3, "../lib/sunbird\n"..., 128)     = 15
read(3, ""..., 128)                     = 0
close(3)                                = 0
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 2469
stat64("../lib/sunbird/run-mozilla.sh", {st_mode=S_IFREG|0755, st_size=10492, ...}) = 0
geteuid32()                             = 1000
chdir("/usr/lib/sunbird")               = 0
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7ed9918) = 2470
close(4)                                = 0
read(3, "/usr/lib/sunbird\n"..., 128)   = 17
--- SIGCHLD (Child exited) @ 0 (0) ---
read(3, ""..., 128)                     = 0
close(3)                                = 0
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 2470
chdir("/home/doni")                     = 0
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7ed9918) = 2471
close(4)                                = 0
read(3, "0\n"..., 128)                  = 2
--- SIGCHLD (Child exited) @ 0 (0) ---
read(3, ""..., 128)                     = 0
close(3)                                = 0
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 2471
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7ed9918) = 2473
--- SIGCHLD (Child exited) @ 0 (0) ---
close(4)                                = 0
read(3, "0\n"..., 128)                  = 2
read(3, ""..., 128)                     = 0
close(3)                                = 0
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 1}], 0, NULL) = 2473
stat64("", 0xbf97315c)                  = -1 ENOENT (No such file or directory)
stat64("", 0xbf97315c)                  = -1 ENOENT (No such file or directory)
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7ed9918) = 2474
--- SIGCHLD (Child exited) @ 0 (0) ---
close(4)                                = 0
read(3, "0\n"..., 128)                  = 2
read(3, ""..., 128)                     = 0
close(3)                                = 0
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 1}], 0, NULL) = 2474
open("/usr/lib/sunbird/init.d", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/home/doni/.mozilla/sunbird/init.d", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/sunbird/init.d/S*", 0xbf97305c) = -1 ENOENT (No such file or directory)
stat64("/home/doni/.mozilla/sunbird/init.d/S*", 0xbf97305c) = -1 ENOENT (No such file or directory)
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7ed9918) = 2475
wait4(-1, Segmentation fault (core dumped)
[{WIFEXITED(s) && WEXITSTATUS(s) == 139}], 0, NULL) = 2475
--- SIGCHLD (Child exited) @ 0 (0) ---
open("/home/doni/.mozilla/sunbird/init.d", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/usr/lib/sunbird/init.d", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/home/doni/.mozilla/sunbird/init.d/K*", 0xbf97305c) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/sunbird/init.d/K*", 0xbf97305c) = -1 ENOENT (No such file or directory)
exit_group(139)                         = ?

####### ende Fehlermeldung ########

Ich habe das mal bei ubuntuusers gepostet:
http://forum.ubuntuusers.de/topic/mozilla-anwendungen-stuerzen-ab-segmentation-/

Vielleicht kann ja jemand anhand dieser Angaben das Problem lösen?!