Version:            (using KDE KDE 3.5.6)
Installed from:    Ubuntu Packages

I've just noticed that KMail hang and was eating all my CPU cycles.

I've attached gdb then and this is the backtrace:
#0  0xb783adfe in free () from /lib/tls/i686/cmov/libc.so.6
#1  0xb79f9d11 in operator delete () from /usr/lib/libstdc++.so.6
#2  0xb7392804 in QStringData::deleteSelf () from /usr/lib/libqt-mt.so.3
#3  0xb7e49c94 in KMail::ImapAccountBase::makeConnection (this=0x860c418)
    at /usr/share/qt3/include/qstring.h:848
#4  0xb7e4b0fb in KMAcctImap::makeConnection (this=0x0)
    at /build/buildd/kdepim-3.5.6/./kmail/kmacctimap.cpp:552
#5  0xb7e5386d in KMFolderImap::slotListNamespaces (this=0x82078e0)
    at /build/buildd/kdepim-3.5.6/./kmail/kmfolderimap.cpp:587
#6  0xb7e76002 in KMFolderImap::qt_invoke (this=0x82078e0, _id=38,
    _o=0xbfd329a0) at ./kmfolderimap.moc:331
#7  0xb70781c4 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#8  0xb7befa6d in KMail::ImapAccountBase::connectionResult (this=0x860c418,
    t0=20, t1=@0xb7552568) at ./imapaccountbase.moc:198
#9  0xb7e4990d in KMail::ImapAccountBase::makeConnection (this=0x860c418)
    at /build/buildd/kdepim-3.5.6/./kmail/imapaccountbase.cpp:287
#10 0xb7e61dfb in KMail::ImapAccountBase::slotSchedulerSlaveError (
    this=0x860c418, aSlave=0x8762c08, errorCode=33, errorMsg=@0x8c0cfe8)
    at /build/buildd/kdepim-3.5.6/./kmail/imapaccountbase.cpp:523
#11 0xb7e61f8c in KMail::ImapAccountBase::qt_invoke (this=0x860c418, _id=9,
    _o=0xbfd32cec) at ./imapaccountbase.moc:284
#12 0xb7e621b3 in KMAcctImap::qt_invoke (this=0x860c418, _id=9, _o=0xbfd32cec)
    at ./kmacctimap.moc:123
---Type <return> to continue, or q <return> to quit---
#13 0xb70781c4 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#14 0xb59ef68b in KIO::Scheduler::slaveError (this=0x8605ec0, t0=0x8762c08,
    t1=33, t2=@0x892bc00) at ./scheduler.moc:153
#15 0xb59ef736 in KIO::Scheduler::slotSlaveError (this=0x8605ec0, errorNr=33,
    errorMsg=@0x892bc00)
    at /build/buildd/kdelibs-3.5.6/./kio/kio/scheduler.cpp:790
#16 0xb5a4dac0 in KIO::Scheduler::qt_invoke (this=0x8605ec0, _id=7,
    _o=0xbfd32e10) at ./scheduler.moc:164
#17 0xb7078097 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#18 0xb59eede0 in KIO::SlaveInterface::error (this=0x8762c08, t0=33,
    t1=@0xbfd32ff0) at ./slaveinterface.moc:214
#19 0xb5a4f4cb in KIO::SlaveInterface::dispatch (this=0x8762c08, _cmd=102,
    rawdata=@0xbfd33030)
    at /build/buildd/kdelibs-3.5.6/./kio/kio/slaveinterface.cpp:280
#20 0xb5a57f0a in KIO::SlaveInterface::dispatch (this=0x8762c08)
    at /build/buildd/kdelibs-3.5.6/./kio/kio/slaveinterface.cpp:173
#21 0xb59fee8c in KIO::Slave::gotInput (this=0x8762c08)
    at /build/buildd/kdelibs-3.5.6/./kio/kio/slave.cpp:300
#22 0xb5a48410 in KIO::Slave::qt_invoke (this=0x8762c08, _id=4, _o=0xbfd33158)
    at ./slave.moc:113
#23 0xb7078097 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#24 0xb70789ae in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#25 0xb740584f in QSocketNotifier::activated () from /usr/lib/libqt-mt.so.3
---Type <return> to continue, or q <return> to quit---
#26 0xb709ac56 in QSocketNotifier::event () from /usr/lib/libqt-mt.so.3
#27 0xb700f2ec in QApplication::internalNotify () from /usr/lib/libqt-mt.so.3
#28 0xb701111b in QApplication::notify () from /usr/lib/libqt-mt.so.3
#29 0xb774bce2 in KApplication::notify (this=0xbfd33804, receiver=0x87621c8,
    event=0xbfd33488)
    at /build/buildd/kdelibs-3.5.6/./kdecore/kapplication.cpp:550
#30 0xb6fa1369 in QApplication::sendEvent () from /usr/lib/libqt-mt.so.3
#31 0xb70016a5 in QEventLoop::activateSocketNotifiers ()
   from /usr/lib/libqt-mt.so.3
#32 0xb6fb6037 in QEventLoop::processEvents () from /usr/lib/libqt-mt.so.3
#33 0xb70299c2 in QEventLoop::enterLoop () from /usr/lib/libqt-mt.so.3
#34 0xb70297d2 in QEventLoop::exec () from /usr/lib/libqt-mt.so.3
#35 0xb7010e95 in QApplication::exec () from /usr/lib/libqt-mt.so.3
#36 0x0804a2de in main (argc=Cannot access memory at address 0x1
)
    at /build/buildd/kdepim-3.5.6/./kmail/main.cpp:110
#37 0xb77e5ebc in __libc_start_main () from /lib/tls/i686/cmov/libc.so.6
#38 0x0804a041 in _start ()