Hi,
This sounds like the wrong Qt libraries are being loaded by the PixInsight Core application. How are you running PixInsight? The *only* valid way to execute the PI Core application is, assuming that you have uncompressed the installation package on your home folder:
cd ~/PixInsight/bin
./PixInsight.sh&
or, alternatively, running the PixInsight.sh launcher script from a GUI file manager (such as Dolphin on KDE 4).
Does this help you?