You need to have KDE (at least kdelibs and kdeui) compiled against the same version of Qt as Designer (so you need KDE compiled against Qt 4.4.3). And make sure Designer's plugin path contains the parent directory of the directory where the plugins reside. You should be able to trick the system into thinking Qt 4.4.3 and 4.4.0 are the same by doing some softlinking. Try ldd on the plugin and see which libraries it expects to find and where it finds them.