MSMQ: Unable to receive some messages

I ran into an MSMQ problem yesterday and I would like to know the reason for this.

I have a server that sends messages to MSMQ and a client that uses those messages. Yesterday, the client stopped receiving one type of message, but was able to receive another type of message that was sent after. I have read some material regarding Poison messages, but this behavior does not match any of the described cases I have seen, because if that were the case, the client would not be able to receive messages coming after the poison message.The problem went away after manually clearing the queue messages.

I also checked the svc log and there were no exceptions.

Any help is appreciated.