You have exceeded the limits of the stack. You have a formula which has more than 12 pending operations. Changing the grouping or the order of the calculations can fix this problem. This limit can be increased in the Mac version by modifying STR# 259 with ResEdit.
KaleidaGraph is a thoughtfully designed graphing and data analysis application for research scientists, as well as for those in business and engineering fields. It produces publication-quality graphs, and easily converts the most complex data into a functional display.