I have a Fishpig/Wordpress installation on my magento site. All works nicely apart from when I look at a child category page. For example if you visit:
http://www.kitronik.co.uk/blog/resources/ then click on a category eg E-Textiles: http://www.kitronik.co.uk/blog/resources/e-textiles-tutorials-resources/
You see that there are no longer breadcrumbs. I can't see why there wouldn't be any for this page?
From looking at your site I can see that you have something custom going on with your breadcrumbs. On the Resources category, by default, the Magento WordPress Integration extension would insert a 'Blog' breadcrumb between the home page and Resources breadcrumb items.
As for the sub-category, the breadcrumbs are pretty much missing completely (other than the home item).
My recommendation would be to check your page/html/breadcrumbs.phtml. If this file is present in your custom theme, trying renaming it to breadcrumbs.phtml.old. This will allow the original breadcrumbs.phtml file to be used from base/default. If this resolves your problem, you know that custom code in your breadcrumbs.phtml was the problem.
Alternatively, do you have a Magento SEO extension installed that modifies your breadcrumbs? If so, you could try disabling this temporarily and seeing whether this resolves the problem.