FusionCharts' debugMode doesn't work when you specify dimensions of 100% by 100%.

Generally speaking, 100% x 100% isn't what you want anyway, as the chart will never shrink or grow even if its container does.  You're forced to recreate the chart when you want to change its dimensions as documented here and here.  So you're better off determining the actual width and height of your container and passing those values into the FusionCharts constructor.

Another gotcha:  the value you use for a setDataXML call is different depending on whether or not the chart has already been rendered!  If the chart isn't rendered yet, you have to URL escape the XML by calling a function like encodeURIComponent.  Otherwise, you can send in XML directly.  So, when re-constructing a chart to change its dimension, make sure you're encoding the XML if you go the XML route!