Arduino and VB

Dear All,
today I tried for the first time to use arduino and a simple program written in visual basic (using visual studio 2010).

From my application to arduino sketch (my application writes and sketch reads) I have no problem, but when Arduino writes on the serial port...my application doesn't read, and remains to wait that the sketch writes something...but nothing happen

Have you some suggestions?

Thanks in advance

(deleted)

At a minimum, you need to post your code - for both sides.