Hey Nobuto,
Your issue is probably a result of termination. When using VISA enabling termination causes the termination character to be stripped off of your read commands. Or, the termination is not being displays. To display the termination right click on the indicator from your read function and select '\' Codes Display.
However, enabling terminatio does not append it back to your write commands. Try appending \n to the end of what ever you are writing. In addition, when you are using hyperterminal do you ever it Enter. If you do then you are sending a \n.
I hope this helps.
JoshuaP