Freeze after switching to Design mode

Sometimes after switching to QML Designer the whole application hangs up for 20-30 seconds and then hangs up for 1-2 second every few seconds. After restarting Qt Creator the problem disappears, which probably means that's not an issue caused by other programs I use. I was able to reproduce this bug few times (but not with 100% reproduction rate) by the following steps:

1. Open an exisiting QML project
2. Open a QML file
3. Switch to Design mode
4. Close the project
5. Create new project using QML Application template and selecting Symbian Qt Components.
6. Switch to design mode on main.qml file of newely created project