Cannot connect to Serial Port

Hi, i'm trying to use serial port with matlab. This is the code that i've used:

     s1 = serial('COM14');
     set(s1,'BaudRate',9600);
     fopen(s1)

This is the message of Matlab:

Cannot connect to the COM14 port. Possible reasons are another application is connected to the port or the port does not exist.

The port is connected because Matlab says:

Available ports: COM3, COM9, COM14, COM16.

With HyperTerminal i can open and use the PORT14. What's is wrong? Thank you for your attention.