Here is an strace in case it's of some use.

mike$ strace firefox
execve("/usr/bin/firefox", ["firefox"], [/* 41 vars */]) = 0
brk(0)                                  = 0x9936000
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) = 0xb77a5000
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=85504, ...}) = 0
mmap2(NULL, 85504, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7790000
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\0000m\1\0004\0\0\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1380932, ...}) = 0
mmap2(NULL, 1391016, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x110000
mprotect(0x25d000, 4096, PROT_NONE)     = 0
mmap2(0x25e000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x14d) = 0x25e000
mmap2(0x261000, 10664, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x261000
close(3)                                = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb778f000
set_thread_area({entry_number:-1 -> 6, base_addr:0xb778f8d0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
mprotect(0x25e000, 8192, PROT_READ)     = 0
mprotect(0x805c000, 4096, PROT_READ)    = 0
mprotect(0x3af000, 4096, PROT_READ)     = 0
munmap(0xb7790000, 85504)               = 0
getpid()                                = 2070
rt_sigaction(SIGCHLD, {SIG_DFL, [CHLD], SA_RESTART}, {SIG_DFL, [], 0}, 8) = 0
geteuid32()                             = 1000
brk(0)                                  = 0x9936000
brk(0x9957000)                          = 0x9957000
getppid()                               = 2069
stat64("/media/sda5/mike_lucid32_on6/mike", {st_mode=S_IFDIR|0744, st_size=4096, ...}) = 0
stat64(".", {st_mode=S_IFDIR|0744, st_size=4096, ...}) = 0
open("/usr/bin/firefox", 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, [], 0}, 8) = 0
rt_sigaction(SIGINT, {0x804f5fb, ~[RTMIN RT_1], 0}, NULL, 8) = 0
rt_sigaction(SIGQUIT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGQUIT, {SIG_DFL, ~[RTMIN RT_1], 0}, NULL, 8) = 0
rt_sigaction(SIGTERM, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGTERM, {SIG_DFL, ~[RTMIN RT_1], 0}, NULL, 8) = 0
read(10, "#!/bin/sh\n\n# Firefox launcher co"..., 8192) = 4569
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb778f938) = 2071
close(4)                                = 0
read(3, "/usr/bin/firefox\n", 128)      = 17
read(3, "", 128)                        = 0
close(3)                                = 0
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 2071
--- SIGCHLD (Child exited) @ 0 (0) ---
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb778f938) = 2072
close(4)                                = 0
read(3, "firefox\n", 128)               = 8
read(3, "", 128)                        = 0
close(3)                                = 0
--- SIGCHLD (Child exited) @ 0 (0) ---
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 2072
stat64("/usr/lib/firefox-3.6/firefox", {st_mode=S_IFREG|0755, st_size=3931, ...}) = 0
stat64("/home/mike/.mozilla/firefox", {st_mode=S_IFDIR|0700, st_size=4096, ...}) = 0
stat64("/home/mike/.mozilla/firefox-3.1", 0xbfc06fd0) = -1 ENOENT (No such file or directory)
stat64("/home/mike/.mozilla/firefox-3.5", 0xbfc06fd0) = -1 ENOENT (No such file or directory)
stat64("/home/mike/.mozilla/firefox-3.6", 0xbfc06fd0) = -1 ENOENT (No such file or directory)
execve("/usr/lib/firefox-3.6/firefox", ["/usr/lib/firefox-3.6/firefox"], [/* 42 vars */]) = 0
brk(0)                                  = 0x928f000
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) = 0xb771f000
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=85504, ...}) = 0
mmap2(NULL, 85504, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb770a000
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\0000m\1\0004\0\0\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1380932, ...}) = 0
mmap2(NULL, 1391016, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x110000
mprotect(0x25d000, 4096, PROT_NONE)     = 0
mmap2(0x25e000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x14d) = 0x25e000
mmap2(0x261000, 10664, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x261000
close(3)                                = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7709000
set_thread_area({entry_number:-1 -> 6, base_addr:0xb77098d0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
mprotect(0x25e000, 8192, PROT_READ)     = 0
mprotect(0x805c000, 4096, PROT_READ)    = 0
mprotect(0x7df000, 4096, PROT_READ)     = 0
munmap(0xb770a000, 85504)               = 0
getpid()                                = 2070
rt_sigaction(SIGCHLD, {SIG_DFL, [CHLD], SA_RESTART}, {SIG_DFL, [], 0}, 8) = 0
geteuid32()                             = 1000
brk(0)                                  = 0x928f000
brk(0x92b0000)                          = 0x92b0000
getppid()                               = 2069
stat64("/media/sda5/mike_lucid32_on6/mike", {st_mode=S_IFDIR|0744, st_size=4096, ...}) = 0
stat64(".", {st_mode=S_IFDIR|0744, st_size=4096, ...}) = 0
open("/usr/lib/firefox-3.6/firefox", 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, [], 0}, 8) = 0
rt_sigaction(SIGINT, {0x804f5fb, ~[RTMIN RT_1], 0}, NULL, 8) = 0
rt_sigaction(SIGQUIT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGQUIT, {SIG_DFL, ~[RTMIN RT_1], 0}, NULL, 8) = 0
rt_sigaction(SIGTERM, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGTERM, {SIG_DFL, ~[RTMIN RT_1], 0}, NULL, 8) = 0
read(10, "#!/bin/sh\n#\n# ***** BEGIN LICENS"..., 8192) = 3931
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7709938) = 2073
close(4)                                = 0
read(3, "/usr/lib/firefox-3.6\n", 128)  = 21
read(3, "", 128)                        = 0
close(3)                                = 0
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 2073
--- SIGCHLD (Child exited) @ 0 (0) ---
pipe([3, 4])                            = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7709938) = 2074
close(4)                                = 0
read(3, "firefox\n", 128)               = 8
read(3, "", 128)                        = 0
close(3)                                = 0
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 2074
--- SIGCHLD (Child exited) @ 0 (0) ---
stat64("/usr/lib/firefox-3.6/run-mozilla.sh", {st_mode=S_IFREG|0755, st_size=10469, ...}) = 0
geteuid32()                             = 1000
getgid32()                              = 1000
getegid32()                             = 1000
getgroups32(0, NULL)                    = 10
getgroups32(10, [4, 20, 24, 46, 104, 115, 121, 124, 1000, 1001]) = 10
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7709938) = 2075
wait4(-1, /usr/share/themes/Human/gtk-2.0/gtkrc:85: Murrine configuration option "gradients" is no longer supported and will be ignored.
[{WIFEXITED(s) && WEXITSTATUS(s) == 1}], 0, NULL) = 2075
--- SIGCHLD (Child exited) @ 0 (0) ---
exit_group(1)                           = ?
mike$