Instrument I/O Assistant Crash

I am using Instrument I/O Assistant to read data from a scale through a Serial->USB conversion, using LV2012 SP1 (I've also tried this on LV2010 with the same results).

I configure the baud rate, parity bits etc, and that seems to work fine.  

I add the "Read and Parse" step or a "Query and Parse" step, and then try to run the Instrument I/O Assistant.  The Instrument I/O Assistant window closes.  It doesn't throw an error, or a warning or anything.  

Needless to say, the vi where I use the I/O Assistant does not run either.

Any thoughts as to why this is happening?