MATLAB & Serial Communication

[Zulo]

Hi,

I've check the forum but can't see a problem like mine..

After Eltima Virtual Serial Port, I can create 2 virtual serial port: COM1 and COM2. And they works like COM1=>COM2. MATLAB sends data to COM1, proteus can see the data from COM2.. it works..

My problem is before i connect the "USB to Serial Device" i can see COM3 available for use. but after i connect the Device MATLAB can not use the COM3..

2 days searching but i can not find any idea to solve the problem. Maybe it is becouse of my device / adaptor.

s=serial('COM3');
set(s,'BaudRate',9600)
fopen(s);
tx='#A';
fprintf(s,'%s',tx);
fclose(s)
delete(s)
clear s

??? Error using ==> serial.fopen at 71
Port: COM3 is not available. Available ports: COM1, COM2.
Use INSTRFIND to determine if other instrument objects are connected to the requested device.

Thanks for help...