Hi,
Which LV version do you have? Can you find the VISION file in Windows Explorer ":\Program Files\National Instruments\LabVIEW 7.1\vi.lib\Version" ?
Which operating system do you use? If you have WinXP with Service Pack 2 try it please to install IMAQ on anoter PC without Service Pack 2. Soemetimes there are some conflicts. Install please on another PC to figured out is it depent on PC.
TN