You need just one QT slot, not both, even w/ USE="qt3 qt4". Patch below:
<snip>
--- kccmp-0.2.ebuild 2007-10-08 16:06:39.000000000 +0200
+++ kccmp-0.2.ebuild 2007-10-28 09:30:53.000000000 +0100
@@ -12,9 +12,9 @@
SLOT="0"
KEYWORDS="~x86"
-IUSE="qt3 qt4"
-DEPEND="qt3? ( $(qt_min_version 3.3.8-r4) )
- qt4? ( $(qt4_min_version 4.3.1-r1) >=dev-libs/boost-1.33.1-r1 )"
+IUSE="qt4"
+DEPEND="qt4? ( $(qt4_min_version 4.3.1-r1) >=dev-libs/boost-1.33.1-r1 )"
+ !qt4? ( $(qt_min_version 3.3.8-r4) )
src_unpack() {
unpack "${A}"
</snip>