Mozill,
Currently the NI-IMAQ for USB driver has not been tested or verified with Windows Vista. Microsoft released a new version of DirectX and DirectShow for Windows Vista. My guess is that some inner workings of these components have changed and in the process caused problems with the NI-IMAQ for USB driver that utilizes DirectShow.
NI-IMAQ for USB is provided as a free tool for customers, but it is not fully tested and supported to the same extent as our official driver releases. With this in mind, any information on Vista support is currently unknown.
Please let us know if you have any further questions or concerns.
Regards,
Luke H