I'm have a very annoying problem with Qt, I can't just drag and drop things to forms. Buttons, input widgets, etc. are unresponsive. Other random parts of Qt's GUI are unresponsive, i.e after selecting technical support the window wouldn't move, close, anything. After running into an unresponsive part of Qt's gui everything becomes unresponsive, even the close window button. I can wake it back up by minimizing it from the task bar but I still can't use many of the features offered by Qt. I've tried googling this and I haven't been able to find anything on it. I want to see if anyone knows anything about this before I try filing a bug report.
I assume you mean the QT Creator IDE? Here is what I would do personally.
First close QT Creator and try restarting your computer to see if that fixes the problem. If not try and see if you can "repair" the program (You know when you go into some uninstallers it gives you the option to repair) if it doesn't do a clean re install instead.
If that doesn't fix the problem contact QT about it.
If you own a commercial version you can contact Digia directly about the problem here http://qt.digia.com/Log-in-Customer-Portal/ otherwise use the support forums http://qt-project.org/forums/ .
Just remember when you submit bug reports you need to include as much information as possible. This includes error logs, ways to recreate the bug, symptoms of the bug, ect. The more information you provide and the more professional it looks the better your chances are that your report will be taken seriously and handled quickly.
Anyways wish you the best of luck and sorry I couldn't be of more help.