Message Queuing has not been installed

[reaway]

When I use MessageQueue to send MQ In ASP.NET, Sometime I can send mq
sucessfully, however sometime I got the exception "Message Queuing has not
been installed". When I encoutered this exception, I change the application
pool of my web application, then it can send successfully again. But this can
not solve the problem, it appears again and again and I must change the
application pool again and again.

I don't know why this exception would occur and I don't know why changing
application pool can solve this problem temporarily. Could anybody help
me?Thanks

My OS Is a new installed Windows 2003 Server (Simplified Chinese Edtion)
The code :

public void SendComStr(string strPath,string data,string strTitle)
{

MessageQueue q = new System.Messaging.MessageQueue(strPath);

q.Formatter=new ActiveXMessageFormatter();
q.Send(data,strTitle);

}