Version:            (using KDE 4.2.1)
OS:                Linux
Installed from:    Mandriva RPMs

4.2.1/Qt4.5

This happens quite often. Kmail is started from menu and just sits there doing
nothing; no UI ever appears. Starting kmail once more usually "kicks" it enough
to continue execution.

bor       5152     1  0 14:04 ?        00:00:03 /usr/bin/kmail -caption KMail

stack trace:

#0  0xb806c424 in __kernel_vsyscall ()
#1  0xb648a6bb in __poll (fds=0x81c8da8, nfds=4, timeout=253698)
    at ../sysdeps/unix/sysv/linux/poll.c:83
#2  0xb4639a8b in IA__g_poll (fds=0x81c8da8, nfds=4, timeout=253698)
    at gpoll.c:127
#3  0xb462c102 in g_main_context_iterate (context=0x81d7260, block=1,
    dispatch=1, self=0x81d1040) at gmain.c:2761
#4  0xb462c3ff in IA__g_main_context_iteration (context=0x81d7260, may_block=1)
    at gmain.c:2511
#5  0xb718351a in QEventDispatcherGlib::processEvents (this=0x81ca070, flags=
      {i = -1076331160}) at kernel/qeventdispatcher_glib.cpp:323
#6  0xb67de75a in QGuiEventDispatcherGlib::processEvents (this=0x81ca070,
    flags={i = -1076331112}) at kernel/qguieventdispatcher_glib.cpp:202
#7  0xb7154c43 in QEventLoop::processEvents (this=0xbfd87e10, flags=
      {i = -1076331048}) at kernel/qeventloop.cpp:149
#8  0xb7155091 in QEventLoop::exec (this=0xbfd87e10, flags={i = -1076330984})
    at kernel/qeventloop.cpp:200
#9  0xb71575f6 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:880
#10 0xb673a0e4 in QApplication::exec () at kernel/qapplication.cpp:3553
#11 0x0804a6b1 in main (argc=Cannot access memory at address 0x4
)
    at /usr/src/debug/kdepim-4.2.1/kmail/main.cpp:146
(gdb) frame 2
#2  0xb4639a8b in IA__g_poll (fds=0x81c8da8, nfds=4, timeout=253698)
    at gpoll.c:127
127       return poll ((struct pollfd *)fds, nfds, timeout);
Current language:  auto; currently c
(gdb) print *fds
$2 = {fd = 3, events = 1, revents = 0}

{pts/2}% lsof -p 5152
...
kmail   5152  bor  mem    REG        8,2   602619  100768 /lib/ld-2.9.so
kmail   5152  bor    0r   CHR        1,3      0t0     239 /dev/null
kmail   5152  bor    1w   REG        8,2   277949   36012
/home/bor/.xsession-errors
kmail   5152  bor    2w   REG        8,2   277949   36012
/home/bor/.xsession-errors
kmail   5152  bor    3r  FIFO        0,6      0t0   16548 pipe
kmail   5152  bor    4u  unix 0xdea95b00      0t0   14788 socket
kmail   5152  bor    5w  FIFO        0,6      0t0   16548 pipe

Quite funnily it seems that pipe is opened inside of the same kmail process
both for reading and writing so kmail dutifully deadlocks.

I do not know how to reproduce it on purpose, but it does happens pretty often here. Startin kmail second time apparently gives it enough of a kick to continue.