Yakuake will sometimes segfault while closing the shell (I use bash) using Ctrl-D. I frequently use Ctrl-D with Yakuake, as it is a nice shorthand way to clear the terminal and start afresh. Normally, Yakuake starts a new shell and everyone is happy, but sometimes Yakuake will crash instead. I'm using KDE 4.5.3 and Qt 4.7.1 I'll try to collect a backtrace next time it happens, I can't get it to do it right now. :\ Last time it happened, though, the KDE crash handler informed me that the backtrace was probably useless.
It's a known Konsole (not Yakuake) bug that will be fixed in KDE 4.5.4. *** This bug has been marked as a duplicate of bug 246652 ***