bfff0011 visa open error

[ptp55]

I am using a usb-to-serial driver interface to a custom device.  I have written some vi's that do a visa-open to the device, sends a query, retrieves the response, then does a visa-close of  the device.  This code was developed using LabView 2012.  When I run this code on a Windows 7 - 32bit machine everything works fine.  I power up the device, launch the VI, get the results, then power down the device.  I can repeat this sequence indefinately.

When I go thru the same sequence, with the identical code on a Windows 7 - 64bit machine this same sequence works fine the first time.  When I do it a second time I get the following error on the visa-open command: -1073807343 (0xBFFF 0011), "insufficient location information or device resource is not present in your system".  I continue to get that error, until I restart my Windows 7 machine.  Then it works the first time again and fails everytime there after.

[crossrulz]

First thing I would check is the USB power settings under the Windows Device Manager.  Windows 7 introduced a "power saving feature" where it will turn off the USB hubs.  That could be messing things up.  My next guess would be a driver issue.

Does the serial port still show up in the Device Manager after running your VI once?

[ptp55]

I will look into the power settings for the usb hub, but I did verify that the device manager was "seeing" the device before I tried to run the vi test the second time.  I don't believe its a driver issue since I have successfully been using this driver on my windows 7 - 32bit machine successfully for over a year.