ShareThis disables flash objects on the page to keep them from bleeding thru our widget's iframe which in some cases will render it unusable. You can turn this disabling off with the "embeds" API option. Append "&embeds=true" to the end of your widget query string.
However, doing this will run the risk I mentioned earlier. You can either be sure to position the ShareThis widget away from any flash objects or choose to have it load in a new popup window. Append "&popup=true" to enable this feature.
You can find more answers to questions involving ShareThis on http://suppport.sharethis.com/ and http://forums.sharethis.com . Also feel free to shoot an email to firstname.lastname@example.org for more direct support.
Thanks for using ShareThis!
Product Support Engineer