Windows 7 - Cannot access USB serial converter

Hi all

I have a USB<->serial converter (several, actually) that I cannot get to work under Windows 7. I know the hardware works.

When I try to open the virtual serial port in a terminal program, I get an error message stating that it cannot open the port. When I try to use the old-fashioned command line method ("copy test.txt com7" from the "DOS prompt"), I get an "Access denied" error message.


Any ideas what the problem can be? I suspect it is some kind of access rights issue. But I need help finding it.


More details:
My computer is a dual-boot Windows 7 Ultimate 64-bit / Windows XP Pro 32-bit system. The USB serial converter worked immediately under WinXP when I rebooted, and it even works in the WinXP virtual machine under Windows 7. I have the latest certified drivers (from FTDI), which are stated to function under Windows 7 64-bit.

The serial converter appears as it should in the Device manager.

My computer has one physical COM port, and I can access that one without any problems.

The serial converter is a USB-RS485-WE-1800-BT from FTDI. I have tried a USB<->RS232 converter (don't have the model number here), but it behaved exactly like the other one. I also started the terminal program as an adminstrator (since I suspected access rights issues), but it did not help.

I have tried uninstalling the drivers, then installing the latest certified driver and the even later non-certified driver, but still had the same behaviour.


So once again: Any ideas what the problem could be? And more importantly, how do I fix it?

... I can add that I also started the terminal program in XP compatibility mode, with administator's rights, but it behaved as it did before.

It appeared to be the mobile phone software, that automatically (and unwantedly) polled the COM port, hogging it for other terminal software...