CPU spikes in firefox 3.5.9

I am using the latest version of open_flash_chart on Ubuntu 10, ff 3.5.9. I am loading graphs dynamically using the technique mentioned here http://pullmonkey.com/2008/09/23/open-flash-chart-ii-javascript-part-3/comment-page-2/#comment-11768.  and I notice everytime I do that, there is big cpu spike in firefox, obviously because of swfobject. Has anyone else seen this?
