Preview = 404 not found

First, please disregard the profile glitch: I am the farthest thing from a WP consultant. If I was, I don’t think I’d be asking for what is probably very basic help.

For some time, I’ve not been able to preview posts before publishing. Yes, I realize there is a plethora of older posts on this subject, and I’ve scanned a great many of them. They don’t seem to precisely apply, though, because I’m not using a plug-in on another website; the blog is hosted directly from WP. — Unless, of course, I’m completely misreading the prior threads, which is entirely possible, I’m afraid. I am also not a geek in this arena.

The version I’m using is, I believe, 3.0.1, but the last digit could be wrong. I’ve seen updates clear through 3.3.1, but I haven’t wanted to risk losing prior content.

The blog was started as a sample to clients how blogging regularly and with relevant content can boost PR and SERP rankings; I’ve not needed it much lately, but I don’t want to have to start all over again if updating the platform loses content.

How can I get the Preview to work again?

Theme: iNove.

Thanks for your help.