Curious spiders? - or - Bad URLs?

[rs2k]

We are getting a very large amount of 404 errors from search engine spiders.

 

Our URLS look like this:

http://www.store_url.com/products_name/product-p-xxxxx.html

 

The problem is that the search engines are trying to go here:

http://www.store_url.com/products_name

 

 

The "referred by pages" in the error logs that have a referrer show the links like this:

<a href="http://www.store_url.com/products_name/product-p-xxxxx.html">Product Name</a>

Is it normal search engine (googlebot is one of them) behavior to try and go to directories they see in URLs? Could this be a problem in how our URLs are formatted?

 

They used to look like this:

http://www.store_url.com/products_name-p-xxxxx.html

 

and we did not get search engines trying to go places they shouldn't.