There is a feature in TikiWiki that you can turn on to force any new Wiki Page to have to be categorized. I searched to see if this same featured existed for other Objects such as Blogs and haven't been able to find it. This means that what you are encountering is probably a bug.
Gary's suggestion would also be my first recommendation to try and upgrade to 3.3. If upgrading is difficult for your team (no IT staff) then create a category and assign it to your blog (remember this is just a quick fix to get your blog running).
Please keep us posted on your progress through this forum post. We will do our best to try and get your site running smoothly.