MSP-FET: MSP430Flasher.exe running in parallel

I am trying to run 4 instances of the MSP430Flasher.exe in parallel but I get occasional errors where it says that the interface is already open. I use the command line option -i to select the unique COM port for the separate MSP-FET programmers, so there shouldn’t be an instance where the interface is already open. In the MSP430Flasher there is code where it loops through each MSP-FET detected, but, I have already tried removing this code without improvement. Has anyone else seen this problem and is there a fix? If only the COM port is used to connect to the tool, it shouldn’t happen but if there is additional USB File I/O in the ‘MSP430_Initialize’ call, it might explain it.