OK, looks like you'll need qt-4.5.3 from testing
Hmm... it looks like it's not enough:
[diego@localhost ~]$ rpm -q k3b qt
k3b-1.68.0-1.fc10.i386
qt-4.5.3-4.fc10.i386
[diego@localhost ~]$ k3b
k3b: symbol lookup error: /usr/lib/libk3b.so.6: undefined symbol:
_ZNK16QAbstractSpinBox16inputMethodQueryEN2Qt16InputMethodQueryE
Regards,
Diego