Bug: Grid lines are in front of bars in Prism 5.0c (mac).

The first tab of the Format Axis dialog lets you specify that Prism draw grid lines at major and minor ticks. These should be part of the axes and so go behind everything else plotted on the graph. This works fine for Prism Windows, but there is a bug in the 5.0c release of Prism Mac: These grid lines go in front of bars. The problem occurs with column bar graphs, grouped bar graphs, and when you plot spikes or drop lines on XY graphs.

Column and Grouped with data points (rather than bars) work fine with grid lines going behind the points -- so long as four or more data sets are plotted on the graph. Box-and-whiskers plots and hi-low floating bars graphs also work fine, with grid lines going behind everything else. 

The bug only occurs with the regular grid lines specified in the first tab of the Format Axis dialog. Additional grid lines added one-by-one in the other tabs of Format Axis work fine. You can specify if these additional grid lines go over or under data, and the default option to go under the data works fine. 

Alternative workarounds:

• Avoid bar graphs. Consider plotting data points. Or consider making a box-and-whisker  plot or a floating low--high graph. Grid lines work fine with these kinds of graphs.
• Specify the grid lines manually. Remove the regular grid lines specified in the first tab of Format Axis dialog. Then go to the Y axis tab and specify additional grid lines one by one. Consider saving your graph as a sample, so its format can be used for future graphs.