Simple Tags Related Posts Feature–Returns Weird Results

I’m using the latest versions of WP (2.5) and Simple Tags (just updated 4/12/8). The Related Posts feature in Simple Tags has never worked consistently for me. It often calls up the same 3 posts, which all happen to begin with the letter “W.” As far as I know that is all they have in common–they don’t have tags in common with each other.

Then every so often a post will have tags that make a little more sense, but not by much.

Has anyone experienced this? Can anyone help me?