This is a common question the SEOmoz help team often receives. In almost 100% of cases, rogerbot (the SEOmoz) crawler, is picking up links hidden on the page.
This is what is great about the PRO platform - it often picks up on problems not visible to the eye.
Two easy way to find links:
- Install the Mozbar and use the highlight link function. If you are unfamiliar with it, watch the video here to get an overview of how it works. This will show you visible links.
- For hidden links, you can use tools like Xenu or Screaming Frog, but in cases like this it's best to view the page source and look for something unusual. Depending on your browser, go to the page and Right Click > View Source.
Also, don't forget universal navigation links. Do you have a drop-down navigation that contains extra links? Also, some website use javascript for fly-out type menus that display links only when users hover over them.
If you're still having trouble, feel free to private message me and I can take a look at your site, or feel free to write the help team (help@seomoz.org)
Best of luck!