Getting onling Mitsch FX2N problem

Hi, We're having a bit of a problem getting online with the medoc program with or new PC's, (Windows XP environment and everything USB)
So we use an serial adaptor - usb adaptor on the com5.
But then he's trying but get's no connection.
I'think it's because the medoc program is DoS-environment and windows OP system keeps occupieing the com-ports, so a dos-program can't make use of the com-ports. Question: is this the problem, and how to solve is, or should it be something else?

I was using USB<>RS232 adapter with just about all Mitsubishi PLCs.
I don't know about MEDOC, but GX Dev works fine...

Some USB adapters work, some don't. See THIS thread...

-Eric