Harene,
A characteristic of LabVIEW is to continually check for the resource. It is not usually an issue with faster machines, but on slower machines this may use up a significant portion of the processor. A suggestion is to have character string passed into a "type cast" with a VISA Resource as the type. This may prevent the machine from continually searching for the device.
Best Regards,
Chris D
Applications Engineer
National Instruments