The "ShareThis" link disappears on mouse hover

I noticed that when using the 3rd party module "ShareThis" which adds a "ShareThis" link to content and content previews, when you hover the mouse over the link, the link disappears (or perhaps turns white on a white background, I am not sure). The link still works, but instead of highlighting the link, it appears to vanish. The little "ShareThis" green icon next to the link remains unaffected.