I created a page to display the tag cloud rather than having a widget in a sidebar. My site's theme is Suffusion 4.2.7 and I used short code
[suffusion-tag-cloud]. There are over forty tags showing but there is at least one missing.
There was a WP thread started by someone else suggesting the original poster use the plugin DB Cache Reloaded. I did that and then my site was sort of broken until I deactivated the plugin. It didn't make the missing tag appear.
I installed a few tag cloud plugins that did make the missing tag appear on the tag page, but they both broke the rest of the site again.
missing tag = Matt Nathanson