Depending on where you got the radio, it might be locked. Meaning, you cant read the radio only write to it. If you are not too worried about the current programming, try and make a simple file and write that to the radio to see if it takes.
I know you said you checked the COM port, but check it again, this is 99% the cause, ever after a person "checks" it.
Are you using a USB opc1122 cable or a serial to USB converter, or is it the serial cable going to a serial port on the computer??
I know with my USB cable, it has had the tendancy to jump around on the com port setting. If I plug it into the same usb port on the computer, sometimes the computer will set it to a different com port number, and I will have to go into "Control Panel- System- Device Manager" to see what com port the cable went to.
Steven