This shows up when, for example, installing the qt sdk under a mount point. Starting Creator returns this error message:
Failed to load core: Could not find 'Core.pulginspec' in Volume

\<path below mount point here>

A simple test program illustrates:

#include <iostream>
#include <QApplication>
#include <QDir>

int main(int argc, char **argv)
{
  new QApplication(argc, argv);

  std::cout << "applicationDirPath: " << qPrintable(qApp->applicationDirPath()) << std::endl;

  QDir d(qApp->applicationDirPath());
  std::cout << "canonicalPath: " << qPrintable(d.canonicalPath()) << std::endl;

  return 0;
}

When run under a normal path, the two lines output are the same. When run under a mount point, the second starts with Volume...