Warpper Qt lib by managed code/c++ for using in WCF broken with Qt 4.8 and higher

[docvu]

Hello,
I have Qt application windows base, I am porting this application to web application. I used the WCF and IIS for development the server side, so i must wapper qt application by managed code /c++ and clr build to dll, then reference this wapper dll to WCF project. In WCF project, i have implemented the interface for calling operations from client. At client side, i used silverlight 4 for developing UI.
The application seem works well with Qt 4.3 to Qt 4.7. However, when i re-compiled with Qt 4.8, we got exception in sometime that exception thrown from QTimer when finished slot completed.
Please see my screenshot at the attachments.
I don't know, if i used Qtimer for logging in runtime? What is impact with EventLoop or WCF? Why this problems are not happen in previous version? What differences in QtCore?
Please help if you have any suggestions.
Many thanks.
Vu