I don't think it's a browser extension because I have tested in Chrome, IE and Firefox, the same problem occurs in all of them. A friend of mine have tested and the ads also appears to her, and also the support staff from my hosting provider have made the same test and the ads also appeared to them, so these ads are shown for every visitor of the blog.
Here are some prints of the problem:
1. Expected behaviour: when JetPack is disabled no Ads show up on top of the blog. This is the expected behaviour, but even when JebPack is enabled these ads shouldn't appear, also. Link: http://lm.eways.ph/7jq
2. JetPack Enabled - Ads Start to Show On Top of Blog: http://lm.eways.ph/7jp
3. More Ads Set when you scroll down. These ones show in Yellow maybe because Google only alows 3 ads per page, the other ones show in yellow: http://lm.eways.ph/7jr
So, as you can see, only when I enable JetPack is that these ads will show up on top of the blog, making my visitors think the blog is only about advertising, since the content will only be seen if the user scrool down until she can see the actual content of the page.
I think someone else has had this same problem as me, but the topic was closed before being solved, so it didn't help much. Here is the link: http://en.forums.wordpress.com/topic/adsense-ads-showing-above-blog-when-jetpack-is-installed