Categories exist, but don't lead to products [SOLVED]

There are a number of categories in my shop (http://onlineshop.yarniapdx.com) that aren't displaying any products, even though there are many products in my shop that have these categories checked under the "Links" tab.

For example, when you click on my parent category "Yarn" from the top menu, you'll see 8 different categories.
http://onlineshop.yarniapdx.com/yarn--

Some of these (Sock Weight, Sport Weight, etc.) will take you to that subcategory when you click on it (and even just hovering over each of these shows you where you will be taken next (i.e. http://onlineshop.yarniapdx.com/yarn--/ ... ing-weight).

However, for 3 of these subcategories (Wool-Free, Solid Colors, and Machine-Washable), hovering over them displays the parent category address of "http://onlineshop.yarniapdx.com/yarn--/ ... ing-weight" and when you click through, takes you right back to the parent category page.

I have scoured these 3 subcategories for any difference but still can't figure out why they're behaving differently than the other 5 subcategories.

Any ideas?

Great images! The products are not related to the problem. I looked at your drop-down menu with Firebug and, as you stated, the last three links are not picking up the sub-category in the address. Just to eliminate the obvious, have you: 1. Checked to make sure you are not using the same seo name for more than one page; 2. Checked to make sure the "Top" box is not checked for the subcategories; 3. In the subcategory page, under data, have you tried deleting the Parent, saving it, and re-inserting the parent; 4. tried setting up another subcategory page under yarn to see if the problem is limited to the last 3 categories, or whether it is something that is now consistently happening under your yarn category.

Usually when I've seen this in the past it's due to either duplicate SEO keywords, or keywords with invalid characters. Check to make sure all your keywords are unique and contain only valid characters.

Wow, @BlueLotusStudio, I guess all I needed was for someone to try and eliminate the obvious! It was indeed your #1 suggestion -- in fact, none of the faulty categories had any SEO keywords inputted (I've never had to input these manually before with the products so didn't think of it). Adding the keywords did the trick and it works fine now!

Thanks for your help!