permalink error

Hi would anyone know how to correct this error I have just started to set up a blog it is still in the testing stage.

I did a test message and changed the permalink to custom /%category%/%postname%/ so that the link would look better for search engines instead of mydomain.com/and the load of numbers puts at the end of the link instead of the category and article name.

The main front page looks fine but if I click the article then the header image and tab images vanish they only show up on main index page.

If I then remove the custom /%category%/%postname%/ the blog works fine.

But then im back to the problem of non search engine friendly links.

Does anyone know of a way to get around around this problem?

Cheers

Ken