I have tried several times to get Pronterface to talk to the Mendel but I get a message stating that it "cannot open port COM3, access is denied". I believe that this is due to a problem in the pronterface code. The Reprap Host Software on my Linux machine had no problem connecting. I think that it is something to do with the communications between the PC and the USB/TTY adapter that leads Pronterface to believe that the COM port has already been opened by another application. I have not been able to find any resolution for this in the various forums.
I am going to install Repsnapper tonight and see if it is able to connect. Good thing that there are a number of options out there for host software.