deleting QListItemWidget crashed which was triggered by another thread

[zeopha]

I created QMainWidget which contains a QListWidget to show log information coming from a socket thread which processed network business. showing log info slots (addLogInfo(const QString &log)) was triggered by a signals in that socket thread . a log item will be created and added to QListWidget every 20 milliseconds.

the signal and the slot was connected in the socket thread's run function with Qt:irectConnection:

connect(this, SIGNAL(addLogInfo(const Log::LogLevel &, const QString &)), parent, SLOT(addLogInfo(const Log::LogLevel &, const QString &)), Qt:irectConnection);

here, "this" is pointed the socket thread object, "parent" is a QMainWidget pointer which pointed to GUI which contained the QListWidget.

in such partern with Qt:irectConnection, I think that the addLogInfo slot was executed in the socket thread(am I right?). In fact, What I want really is that the slot was executed by QMainWidget thread itself which can be done through Qt::QueuedConnection. But when I set connect function with Qt::QueuedConnection, it will complain:
"QObject::connect: Cannot queue arguments of type 'Log::LogLevel'
(Make sure 'Log::LogLevel' is registered using qRegisterMetaType())

But I don't know how to register my user-defined type Log::LogLevel, such statement:
qRegisterMetaType<Log::LogLevel>("LogLevel") won't work. Log is:
class Log
{
private:
Log();
~Log();
public:
enum LogLevel {Debug=0, Info=1, Warning=2, Error=3, Fatal=4};
};

when QListWidgetItem number in QListWidget is more than a threshold (such as 50), QMainWidget will delete the first QListWidgetItem in QListWidget through the statement "delete lsgLogInfo->item(0)" located in the slot.

After deleting item several times, the program will crash with following gdb info:
ASSERT failure in QVector<T>:perator[]: "index out of range", file ../../include/QtCore/../../src/corelib/tools/qvector.h, line 324

In fact , I inserted a statement "printf("count=%d\n", ui.lstLogInfo->count());" which printed the count is the threshold plus one. So , the deleted index equal to 0 will not be out of range. But the crash really happened.

anybody can help me?
any help will be appreciated!
thx!

[jpn]

Please do not cross-post.