I recommend posting this question on the Vision discussion forum, as there are many more IMAQ users who may have experience using Borland C with NI framegrabbers. Here is one such discussion thread that you might find useful: http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RNAME=ViewQuestion&HOID=50650000000800000048100000&ECategory=Vision.
Otherwise, contact NI Technical Support for further assistance.