Custom characters created using Private Character Editor (eucdedit.exe) on Windows 7 are not working with Qt4 while those were working with Qt3. With Qt4 it shows a unfilled square and with Qt3.3.8 it shows the real character. Please note, that if you copy+paste the Qt4's unfilled square to some texteditor (which uses utf8) it shows the character correctly (which means that Qt4 draws the unfilled square for a known character).
I attached a simple test application to reproduce the issue. The application reads a character (0xE000) from a text file and puts it to a QLineEdit widget.
Before running the test, you need to create your character using eucdedit.exe (installed by default on windows 7), as you can see in eudc.png. Screenshots qt3.png and qt4.png shows the issue.