can you please specify which technology you are currently using ... i mean asp/php/asp.net/cf/ruby etc. or simple HTML & JavaScipt.
You may try these out :
1. make sure you have used RegisterWithJS option on..from renderChart() method/ FusionCharts() JS constructor.
2. If you have placed the chart inside a FORM element ... please use this new FormBugFix (beta) version of FusionCharts.js :http://www.fusioncharts.com/forum/Attachment152.aspx