Content triple display on top of page

I have an odd problem that I wasn’t able to find earlier in the forum. I have content that sometimes displays 3 or 4 times on the page. This happens no matter what theme I install, and it only seems to happen with plugins. A good example can be found at my store. Here, the shopping cart is visible once where it’s supposed to be, and 4 times at the top of the page. On other pages, like my forum, I’ll have user content once within the forum and two more times on the top of page. If I receive a message from another site user I also get 3 emails with the same content. Any help would be greatly appreciated.