Serial port not available

Hi all,

I'm trying to connect a GPRS modem (Siemens MC35) to my windows CE based
device (platform smdk2443 Samsung).

I have  for UART possible ports:
UART0 -> I'm trying to connect my GPRS modem on it
UART1 -> Debug port
UART2 -> not available
UART3 -> I've also tried on this one

the problems is that I follows all the steps to create a dial-up
connection
but when I execute it I obtain the following error:

This port is not available: maybe another program is using it


I have delete from my Operative System image all functionalities that
could be using COM1 port (UART0) (also if I'm sure they're not using it),
I've verified that serial port is defined on system registry and I've
verified that debug port is UART1....anyway I still get this error and I'm
completly lost...

Could anyone help me???????

Thanks a lot in advance!!!!