Are you stopping the VI and acquisition using the "STOP" front panel control before attempting to close the VI? Doing so should allow the IMAQ Dispose VI to properly destroy your image and free up the memory space that image was occupying.
Also, in general it is safer to use a ring rather than a grab (see LL Ring.vi). A grab acquisition uses only one buffer, so it is possible that the buffer could be overwritten while in the process of copying the data out of the buffer. A ring acquistion works in the same as a grab, but multiple buffers are used instead of just one. This could be useful in situations where copying of the buffers may be slow.
Also, what version of NI-IMAQ are you using? If you do not have the most current version, NI-IMAQ 2.6, I suggest you
upgrade to this version of the driver at http://digital.ni.com/softlib.nsf/websearch/50F6D6F1094A033586256D52006146E0?opendocument&node=132070_US.
If the problem persists, please contact NI technical support for further troubleshooting.
Best regards,
D. Putnam
Applications Engineer
National Instruments
