Cannot run server correctly in Debug

[KalaShayminS]

Enviroment: Qt 5.0.2, MinGW 4.7, Windows 8.1, Debug mode
Problem: Server automatically closed after someone logged in at tier.cpp:720 when setting the tier.

void Tier::processQuery(QSqlQuery *q, const QVariant &name, int type, WaitingObject *w)
{
if (w) {
w->setProperty("tier", this->name());
}

Error:
ASSERT failure in QCoreApplication::sendEvent: "Cannot send events to objects owned by a different thread. Current thread 225f5030. Receiver '' (of type 'WaitingObject') was created in thread 19ae7df8, file kernel\qcoreapplication.cpp, line 420

In Release it works, but this makes me confusing and cannot debug any more.