I had the same problem, but I have corrected it. My problem is I forgot set 'registerWithJS' flag to 1 instead 0.
Make sure you specify:
var chart1 = new FusionCharts("../../FusionCharts/Column3D.swf", "chart1Id", "400", "300", "0", "1");
not:
var chart1 = new FusionCharts("../../FusionCharts/Column3D.swf", "chart1Id", "400", "300", "0", "0");
Please notice different between the last value of two statement above (1 vs 0). When I change the last value from 0 to 1, function saveAsImage() work fine.