Hi,
Take a look at this document:
http://digital.ni.com/public.nsf/websearch/FCA602CDBC4EDCEA86256BB1005AB1F2?OpenDocument
This limit is no longer a issue in NI-IMAQ 3.0.1, (except for the NI-1408)
Met vriendelijke groet / Kind regards,
Karsten
Applications Engineer
National Instruments