Multi thread problem

[jacek]

Then if an operation is already running in gui, the gui crashes

So you have to either wait for the GUI to finish or make the GUI delete those objects when it doesn't need them anymore.

[ball]

http://doc.trolltech.com/4.1/qobject.html#deleteLater

for any object that are extend from QObject, use the deleteLater function rather than directly use the [delete] operator