Opening a specific .ui file in designer, closing it, then opening another causes segfault

In a project with a number .ui files, opening any of them after the attached mainwindow.ui file causes QtCreator to segfault.

In the project, I can successfully go into design mode on any of the .ui files. However, after successfully going into design mode with the attached mainwindow.ui file, attempting to use any other .ui file causes a segfault (after a few seconds). This does not occur when mainwindow.ui is the next .ui file I use - I can open and close mainwindow.ui as may times as I like in succession, but after using it, any other .ui file (which would previously open successfully) causes the segfault.

This problem didn't exhibit itself in beta 2.

Steps to reproduce:

1. Create a project with multiple .ui files, including the attached mainwindow.ui file
2. Open the project in QtCreator
3. Double-click the mainwindow.ui file to enter design mode
4. Close design mode
5. Double-click any other .ui file to enter design mode