InputAssistant component not active: We have been working with the "temporary" license file without problems and now want to switch to the unlimited license file, since we are using GuiXT 2015 Q1 3. But the component "InputAssistant" is not active with this license file. We have checked that the license file itself includes the component. What could be the reason?

You probably did not include the system specific license key in your guixt.ini file ("Key ..."). This is not required for a temporary trial license but it is for a permanent one.