I think it has something to do with technical issues. And going to the thread that charles tim mentioned is the best choice since most of the bitcoin geek are in bitcoin and technical support. If there is a wrong with your transaction, I think when copy pasted the address. But I am not sure that it would happen as you said, you always double check the address you input. It is somehow scary if there is an issue like this, it is not safe to send when there are bugs in wallet. I don't know how to deal with this because this is my first time to encounter such problem like this.