QString exception while executing assignment operation

Good morning,
I have a problem using QT 4.7.1 on a Wince Arm platform (pxa270).
I cross compiled some year ago the qt libraries, and I'm using them for the business logic section of my SW project.
I use the Qstring class in many sections of my code, but sometimes I get an exception at run time.

I found, for example, that this line of code

QString createdDateString= QDate::currentDate().toString();

Sometimes generates an exception.
If I modify my source code (also different section of the SW), the exception sometimes disappear.
Similar errors appear at run time when I use code initializations like that

QString a = "test"

Do you have any hint about this topic?
It seems a memory leak bug in my code, but I can't find where.
Best regards
Giovanni

In most cases when something like this happens, the object this code runs on, i.e. the object for which the surrounding method is called, is not valid (anymore).

Cheers,
_