Philippe: In this case it isn't really about arg1 at all. The resource you passed into the Configure VI (presumably something like COM1 or ASRL1::INSTR) is busy - the error is VI_ERROR_RSRC_BUSY. This means that you most likely have some other application using the resource, like Hyperterminal.
For what it's worth, the property node refers to each property in order, so the first property inside the Configure VI is the timeout. This is the first point at which that VI needs to use the resource you passed in, so that's when it tries to open the VISA session and fails. So it failed when trying to do a 'set' on arg1 because in this case it couldn't open the resource. Dan Mondrik National Instruments
